Michael Rechenberg
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Trying to get correct cycle detection

Does

bool graph_adjacent(graph *this, void *s, void *t);

Does this function return true if there is an edge between the two vertex which can either go from s to t or t to s or does it only return true if there is an edge from s to t

parallel_make

edit · good question 0

Updated 5 days ago by Anonymous and Asad Quddus

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the students' answer,

where students collectively construct a single answer

An edge from s to t since it's a directed graph.

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edit · thanks! 1

Updated 5 days ago by Anonymous

the instructors' answer,

where instructors collectively construct a single answer

The latter. It checks for the edge ('s','t') and not ('t','s').

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thanks! 1

Updated 5 days ago by Navneeth Jayendran

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4/6/17

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Instr Listening on Chatroom

Chatroom Lab has been Released!svn up and you get the chatroom directory.You can find the docs here This lab is due on 4
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4/5/17

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Instr Autograder MP Mapreduce Released

The AG for MP Mapreduce is released! Schedule: "2017-04-05 22:00", "2017-04-06 22:00", "2017-04-07
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4/4/17

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Instr Know Your Tools Graded!

Hey Everyone, Know Your Tools grades are up on Chara Gradebook! Sorry for the delay! The grades were calculated 50% Kn
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4/3/17

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Instr May the 4th be with Your Second Chance Assignments (~~Regrade Requests)

Dear CS 241 Students, The long-awaited post you've all been desiring! We know that system programming is unforgivi
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4/2/17

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Instr Mapreduce: More Piping, More Reducing, "Same Great Taste"

The mapreduce mp has been deployed to you all. You can find the docs here. This mp is due 4/10 @ 11:59pm Please u
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2/28/17

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Instr Community Matters

With us moving towards the midway point in the semester and with everyone’s work load increasing I want to remind you al
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2/8/17

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Can you use gdb to debug child processes?

I set a breakpoint in gdb in a section of my code that only a child process would have access to, but when i ran gdb, th

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9:17PM

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Closing pipes and dup2

I'm so sorry for taking up your time :/ but there's something about pipes that I'm really confused about. W
8:59PM

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splitter error: tried to write ... bytes, wrote 0?

I'm just trying to get the splitter to work right now. I have a pipe for each mapper and I'm calling fork, dup,
6:52PM

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How does the server react when a client closes its connection?

So the server accepts no more than 8 clients. Just to clarify, does this mean that once we have accepted 8 clients, we
4:33PM

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hang when running with debug build

My code worked fine when I ran ./mapreduce data/small.txt test.out ./mapper_asciicount ./reducer_sum 3 But when I ran it
4:22PM

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Quiz 5 topics?

What topics will be covered on quiz 5 next week?
2:54PM

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Exec for mapper

Wondering what the exec command will be to send the output of the splitter to the input of the mapper. I know we'll
2:27PM

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When will Final Exam conflicts open up?

Everyone in MATH 415 knows that its final exam is at the exact same time as this one. MATH 415 has begun conflict exam s
1:34PM

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get_message_size returns 0 immediately?

I've been trying to get my chatroom working and I've noticed that when my thread calls get_message_size, it retu
1:08PM

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Testing mapper_pi

I believe it should be updated in the docs that the way to run pi/create_pi_input.py 1000000 > in should instead be
11:57AM

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what are we supposed to do for "Print nonzero subprocess exit code"

What are we exactly supposed to below this comment on the MP?
10:23AM

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Couldn't open/read output file?

On the autograder run, I pass "multiple mappers" and "splitter usage", but for some reason on all the ot
10:15AM

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Definition of 'fixed size'

For the midterm, we are required to implement a 'fixed size' memory allocator. Does 'fixed size' refer t
10:12AM

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resolved
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Instr Saturday 10-12 PM OH Moved

Hi, I will be moving my office hours from Saturday 10-12 to Monday 12-1 and Tuesday 5-6 for this coming week. Apologies

▾ Yesterday

11:41PM

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test server down?

Is the test server down? I cant seem to connect with my client or the client reference. Thanks :p
11:26PM

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Autograder Timedout

The autograder timedout for every test. all the tests run though. is there a likely reason for this.
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11:21PM

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print_usage

On which occassions/input would we use print_usage to tell the user to try a different input?
11:16PM

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memory leak in getaddrinfo

So I do freeaddrinfo the linked list res but somehow Valgrind keeps saying I have leaks in ==15703== 64 bytes in 1 bloc
11:14PM

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Running execl

execl("/splitter", "splitter", "data/small.txt", "3", "0", 0); I tried running e
10:55PM

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read()/write() with dup2

After using dup2 on a file descriptor, we don't need to call read or write on that descriptor right? Cos the stdin/s
10:39PM

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Question about how we do networking

So oppose to how the lab chatroom is designed, where we read only as much as it's written by reading the first 4 byt
9:35PM

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Bad file?

For some reason the file I get from argv just will not open. I have tried using fopen and open and both do not successfu
9:25PM

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print non zero subprocess exit codes

Should we make an array of every exec that failed, and call print_nonzero_exit_status() on each element?
9:23PM

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Sequence of waitpids

So, I noticed in the comments in main that the only mention of wait is //wait for the reducer to finish Does this mean
8:41PM

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return value of read_all/write_all

In utils.h, it says return 0 if socket is disconnected, but the docs say "Let y = read(x bytes), if y == 0 then conn
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8:00PM

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How to call mapper function?

Hello! So my current strategy is using fork() and running splitter function in the parent process and mapper function in
5:12PM

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solved

solved
5:12PM

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solved

solved
4:58PM

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pipes for splitter stdout

I create as many pipes as I have map counts, and then in a for loop, fork. In the child process I copy the stdout to the
3:42PM

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Using the splitter

Hi guys, I'm a little confused on how I should be calling the splitter in the main function of mapreduce.c. As of n
3:33PM

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Not written to output file

I created the output file and give it permissions. Now when I run commands, the output is written to terminal rather tha
3:03PM

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Do we need fork() to run reducer process?

Hello! I notice that the reducer process is executed after all mapper processes are finished and all Key Value pairs are
2:47PM

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Unnecessary Multi Threading

multi.mp4 Finding Credits: Shreyas Patil
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1:33PM

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midterm2 question

The handout says that we need to implement a fixed size allocator. I am wondering will the exact size be told during the
1:30PM

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splitter not producing equal size files?

I was just messing around with the splitter in my command line, and I tested out ./splitter data/small.txt 3 0 which o
1:14PM

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A small question about exec

Hello! I just wonder where I get my execlp function wrong... execlp("./splitter", "./splitter", "tex
1:11PM

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How to create many pipes?

Hello! I wonder whether I can create an array of pipes and use a loop to call "pipe" on each element. Is this a
12:29PM

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How to pipe mappers to reducer?

Hello! I am a bit confused about piping mapper to reducer. Since we have many mappers but one reducer, can I give each m
12:11PM

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Quiz 6

CBTF is showing sign up for Quiz 6 but according to the syllabus there are only 5 quizzes. Is there a quiz 6?
10:41AM

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segfault if there is no output file

I got segfault when I run the given example if there is no output file. ./mapreduce data/alice.txt test.out ./mapper_
1:47AM

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Malloc

Ideally, would a non-block-coalescing and O(n) version of malloc pass the first 7 tests from the MP?
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12:50AM

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Class Transcribe

Are there plans to do transcriptions for this semester's lectures, and if so, would that be offered as an extra cred
12:25AM

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what would an output file look like?

will it just be an list of output chunk just like above? Is there a sample output file?

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Wed

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Unable to Open/Read Output File

In the mapreduce auto grader, I've failed the performance and small input test cases with the error message "Una
Wed

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examples.sh

Not sure if anyone else is having this problem but sometimes when I run ./examples.sh I get that I pass all of them but
- 1 Unresolved Followup
Wed

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Timeout on Large Input

I passed all the other tests including the performance test, but timeout on the large input test. What might be the pote
Wed

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execing in mapreduce

Would it be more fitting to use execlp() in this case?
Wed

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getting the idea right (mapreduce)

Is it supposed to work like the image? So, do we first have to grab the result of the splitter and then send it thr
Wed

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SJF issues

I am running into the issue that while a job is running, a shorter new job comes in and goes to the front of the pqueue.
Wed

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Response time

Just want to clarify, so the response time begins as soon as the job is pulled of the queue? And for pre-emptive schema
Wed

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Small differences in average response time?

I'm getting average response times too low on PLRTF proc 2, PLRTF proc 3, and PPRI proc 3. The differences are 1.2s,
Wed

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Compiled on vm but not on autograder for 2pm autograde

Issue was did not recognize vector, but I had #include vector.c and it compiled on my machine. are we not allowed to use
Wed

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Example Queue not printing?

The "Queue" part of the example output is not printnig when I run the simulator. Everything else seems be printi
Wed

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Possible Bug With Lecture Code

void* mem = allocate(100); Block* b = mem - sizeof(Block); Should the second line be Block *b = mem - 1 instead, since b
Wed

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splitter behavior

I am not sure how splitter works. When I try to call this on the file that has Hello there class! and use ./splitter
Wed

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Different Times

can somebody elaborate what wait time and turnaround time is?
Wed

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proc2-rr1.out ????

=== [TIME 2] === Job 0 had its quantum expire. Processor is now running job 1. Queue: 1(0) 0(-1) A new job, job 2 (r
Wed

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order of jobs in priority queue

For some of my schemes, the order of the priority queue is reversed for just a few of the iterations. e.g. for SJF, tim
Wed

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How to check if processor is idle?

if it is returning -1
Wed

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AG Tests for Round Robin

I have every other aspect of the lab done except for the average response time calculation (which I just set to 0 as a p
Wed

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Peculiar Output

I am not sure what to make of this output when I run the simulator for proc1 in PPRI: Loaded 4 job(s) using scheduling.
Wed

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How would I execute a job after the latest one finished?

Im looking through the files and I don't see any functions related to executing the job. So im not sure if i were to
Wed

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resolved

resolved
Wed

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A tricky bug about timing of calling job_finished and new_job

Hello! I notice that the timings of calling job_finished and new_job are both at the beginning of a time unit. For examp
Wed

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Priqueue as Normal Queue

So I looked at the docs and I changed the comparator so that the priqueue should behave like a normal queue for RR. Afte
- 1 Unresolved Followup
Wed

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Any hint about scheduler_clean_up?

Hello! When I am thinking of scheduler_clean_up function, I only use malloc in scheduler_new_job to create new jobs and
Wed

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Instr Cancelling Today's Office Hours

Hello everyone, Sorry for the inconvenience, but I'll have to move these hours to 12-1pm and 3-5pm on Friday. Rega
Wed

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Different output when printing to stdout/redirecting to a file

When I run: ./simulator -s PRI examples/proc1.in I get the correct output (same as in proc1-pri.out), but when I redirec
- 1 Unresolved Followup
Wed

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networking mp

Is our last mp going to be split into 3 parts ?
Wed

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Can't ssh

Nvm, it works again.
Wed

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Is Networking worth 3 times a normal MP?

The website is saying it is a 3-week MP and the prospect of it being worth 3 times a normal MP is giving me the creeps.
Tue

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job -1

in ppri, there is when Job 0 finished, the processor runs job -1. But I didn't seem to see any new job -1 arriving
Tue

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Topic question

Is the first part of the midterm multiple forks or is it threads? I was a little confused by the wording on the handout.
Tue

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sol
Tue

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plrtf

Just to clarify, this just means we compare the runtimes? Since we'd update the runtime if a job is only partially r
Tue

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Queue memory

In the queue are copies malloc'd when things are inserted? i.e. should we free jobs after pushing? Or should we only
Tue

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Average Response Time for round robin

I keep getting off by a couple decimal places on round robin's average response time. Right now in the quantam funct
Tue

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arrival_time

May we assume no two jobs have the same arrival time?
Tue

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difference between rr and fcfs

So in my comparer_rr I'm comparing arrival times, just like in my comparer_fcfs. Turns out this is wrong: my result:
Tue

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scheduler_new_job()

for one specific job, for example in RR, is it possible that scheduler_new_job() called on it several times? if not, the
Tue

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Queue Purpose

So from my understanding now, the queue exists just for us and the simulator doesn't ever need to see it. If this is
Tue

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How to maintain the job priority queue after adding a job at top?

The title could be confusing, sorry about that. What I am struggling with is that under the case that a new job is added
- 1 Unresolved Followup
Tue

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how to force a element to the end of a priqueue
Tue

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Why parameters for finished_job?

Seems like we are just supposed to check if another job is next. Why do we need to know the job number and time, assumin
Tue

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new job clarification

When you create a new job, to determine if it should be run, do we call the comparer function of the new job and the hea
- 1 Unresolved Followup
Tue

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Job_finished/quantum_expired

Should we assume that when these are called the onus is on us to remove the job from the queue? i.e. we should assume we
Tue

11
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New_Job question

from Libscheduler.h: @return True if the job is to be scheduled immediately. False otherwise. Does "to be schedu
- 1 Unresolved Followup
Tue

2
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examples.sh

If we don't implement scheduler_show_queue would examples.sh still work? Edit: yes.
Tue

4
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How to access member data in comparater functions

When I try to implement comparison functions, int comparer_fcfs(const void *a, const void *b) for example. I think "
Tue

7
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Removing from the pqueue

When I run something like ./simulator -s PRI examples/proc1.in How am I supposed to remove a job that has been running
- 1 Unresolved Followup
Tue

11
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how to get the scheme?

I want to do something different in scheduler new job when the scheme is ppri or plrtf, but setting scheme = s in schedu
- 1 Unresolved Followup
Tue

7
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Arrival Time?

Does anyone know how to find this?
Tue

2
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Response Time Calculation

I'm still confused about how to calculate the response time for preemptive. For example, when I'm doing the proc
Tue

2
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int comparer_fcfs(a,b)

for int comparer_fcfs(a,b), what if the arrival_time of a,b are equal? in this case, we return 1 or 0 or -1?
Tue

2
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Where to initialize global curr_job?

I have a global curr_job variable for the purpose of round_robin and other things in my implementation. I am not sure wh
Tue

2
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regrade malloc

Does it mean if I choose malloc I can only choose malloc?
Tue

2
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why the core_t given is empty? do we have to add attributes?

/** * Sores information on how one core is being used. */ typedef struct _core_t { } core_t;
Tue

2
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Arrival?

Nvm
Tue

2
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Resolved
Tue

0
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Printing Return Value of Mappers

In the docs it says we should have something like my_mapper 0 exited with status 1 whenever the mappers exit with a non-
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Tue

1
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Sending EOF to Mappers

I'm a bit confused as to how we send the EOF character to our mapper sub-processes after we pipe the output of the s
- 1 Unresolved Followup
Tue

18
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Incorrect average response time for proc3 with ppri.

According to proc3-ppri, average response should be 77.39, but my average is 75.72. Did anyone else get this wrong as we
Tue

1
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Instr 5 - 6 PM OH Cancelled Today

I won't be having my 5 - 6 PM office hours today due to a midterm.
Mon

0
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quantum/job arrival

If the quantum expires at the time when a new job arrives, will new job function always be called first instead of quant
Mon

2
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Question regarding core struct

Can we modify the core struct to hold the present job? Thanks in advance
Mon

2
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Does this mean I am not busy waiting?

Title
Mon

0
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testcase4

With (threads == 2), two of the three Stage #3s should run at first. If Stage #3(b) runs during the first batch, it wil
Mon

0
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quantum in scheduler?

In the function int scheduler_quantum_expired(unsigned time), how do we know the quantum time? Are we supposed to keep
- 1 Unresolved Followup
Mon

0
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Knowing When Tasks Switch In/Out

Is there any way for us to know when tasks are switched out? Knowing that seems instrumental in implementing Pre-emptive
Mon

0
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Job Start Time

How are we able to figure out when a given job actually starts? It doesn't seem like any of the functions we write a
Mon

0
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simulator confusion

Since in scheduler_new_job only a boolean value is returned, and in scheduler_job_finished the id of jobs is return, how
Mon

0
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role of example output files?

Example output files: examples/proc1-fcfs.out: Sample output of the simulator, using proc1.in and FCFS scheduling.exampl
Mon

4
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scheduler_quantum_expired

Is it possible for scheduler_quantum_expired to return -1? Based on the document I can not figure out any example that t
Mon

4
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sjf ppri pri clarify?

pri: === [TIME 4] === A new job, job 1 (running time=6, priority=1), arrived. Job 1 is set to idle (-1). Queue: 1(-1)
Mon

0
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Passed throughput test before but got 2/4 now

what was the possible reason for this case? I passed this test before. But for the newest ag, I got one timeout message
- 1 Unresolved Followup
Mon

2
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Some thread doesn't stop waiting even after calling broadcast

So this is my debugging printfs for [./parmake -j 3 -f test_makefiles/testfile1] main in cycle detection - curr:pushing
Mon

0
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Hard Test Failure due to Time/Memory Error?

Has anyone else been failing the "hard test" with a time of around 0.005 seconds? No matter what I do, I keep g
- 1 Unresolved Followup
Mon

0
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Bug not detected by AG

My code deadlocks when running testfile7 where a dependency fails if there is only one thread, and still passed the AG.
Mon

2
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condition not working as intended

So I have debugged with gdb and found out that when I cond broadcast when my worker threads are waiting at the cond wait
Mon

20
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hard test fail: reason file

does anyone have the few output error msg due to the file?? I really appreciate if someone could give me a hint
- 3 Unresolved Followups
Mon

4
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How to test if multithreading improves my time below the autograder limit?

im thinking that because im using mutex locks within my threads my time isn't going to improve significantly and I w
Mon

3
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Topics

What topics/weeks will be covered on Midterm 2?
Mon

2
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error related to return value

does the following function return the keys of the vertices inside the vector or pointers to the rules itself? vector
Mon

16
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Too few outputs, I have a theory! Let me know your thoughts!

a: b c d echo "This will not run" b: cat adsf echo "This will fail, should not see" c: random1 echo
Mon

2
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No Threading in Mapreduce?

Not trying to make the MP harder, but wouldn't Mapreduce run faster if we ran all the splitters in parallel, then ra
Mon

9
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Hard Test Timeout

When I run testfile4 with 3 threads I get about 18 seconds and then close to 0s for user and sys times. But I am still g
Mon

0
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Too many lines of output!

I got a lot of "too many lines of output", but I am sure my local tests are good. Does files depending on newer
Mon

0
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Circular Dependency Tests

Does anyone know if circular dependencies are tested in any other test other than Hard Test?
Mon

3
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throughput test

Hi. so I just saw my result and saw the following for throughput test: <code>Trying to compile your code... Succes
Mon

0
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Hard Test- too few lines of output?

Hi, I have been failing this test and getting the "too few lines of output" for the whole week and have tried to
Mon

4
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Hard test--> Too few lines of output

I get a zero for the hard test and I can't seem to figure out way. It keeps saying "too few lines of output."
- 1 Unresolved Followup
Mon

0
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Queue stalling inspite of pushing nulls?

I am confused as to why my queue is stalling (output is correct), even though I push threads-many NULL elements at the e
Mon

0
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Getting Time in comparator functions

I am a little confused on how to get the arrival time when writing the comparator functions. I was thinking of adding th
Mon

0
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round robin

How do we "take something off the core" for round robin? I assume that every time scheduler_new_job is called fo
Mon

0
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testfile5

one follow up says There's two ways to interpret it, which will both be considered correct for grading purposes: I
- An instructor thinks this is a good question
Mon

3
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hard post?

Why is hard test worth two full letter grades? It is based on "full parallelization" something that is basically
Mon

5
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solved
Mon

11
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Can there please be a 6 PM autograder run today?

Especially since there were so many autograder runs for Part 1? That would be immensely helpful.
Mon

8
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Weird Memory Leak??

When I run valgrind, I am getting 4 of the following leaks: Any idea where those could be coming from? Because it doe
- 3 Unresolved Followups
Mon

2
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Freeing vector returned from graph?

For the vectors that are returned from the graph, do we simply have to call vector_destroy() on the vectors? Or do we al
Mon

5
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Is this correct output?

I struggled a lot to make my recursive run_dependencies function iterative and queue-based. Now it is finally giving all
Mon

0
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Still timeout!!!

I got 15/17 in part1 and I worked a lot time with part2, but I still get "time out" from every test. I have chan
- 2 Unresolved Followups
Mon

0
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Printing Failed Subprocesses in Mapreduce

In the given mapreduce file, it says that we should, Print nonzero subprocess exit codes However, I don't see that
Mon

3
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hard text maximum parallelization

A reverse topological order cannot guarantee maximum parallelization, and the execution time of each rule is needed to d
Sun

0
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Weird question about the queue pull

When I use queue pull to pull the node one by one and execute each one, I am expecting the queue to give me each element
Sun

0
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Mapreduce hanging on large files

I was testing mapreduce functionality and it seemed to work fine for the smaller files (small.txt and asciicount1.txt) i
Sun

7
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Scheduler Response Time

"When calculating response time, you should not consider a job as responded until it runs a CPU cycle." how do
Sun

0
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graph_get_vertex_value

I created a queue of char *. It will make a deep copy of each vertex (char *target name). In my thread function, it gets
Sun

0
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Autograder Timeout

Would we be timing out on the autograder because we'e using too much CPU time or is it specifically to test that our
Sun

4
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timeout for hard_test

I have pass all tests except "hard_test". I get timeout for it. Can someone tell me where the problem might be?
- 2 Unresolved Followups
Sun

0
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priority index

Hello, I am wondering that for the savage scheduler lab, is that true that the higher the value is, the lower th
Sun

4
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hard_test

I got Too few lines of output! and Reasons: file on the hard_test. I checked the flow chart several times and still co
- 1 Unresolved Followup
Sun

0
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Cores and core_t?

What exactly am I supposed to be using the cores for in the lab? I see the struct but I'm not sure what I'm supp
Sun

3
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Virtual Memory

Why is it bad to have really large page tables? What is the mechanism used to reduce the size of the page tables? For a
Sun

7
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use condition number to prevent busy wait

So I'm using condition number, but still get this performance, so I think I might have use it inefficiently real 0m1
- 1 Unresolved Followup
Sun

3
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Parmake Autograder Changed?

I was getting every test correct except for a 4/5 on the hard test due to "Reasons: file". I didn't change a
Sun

4
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Why do my threads not join?

While debugging with GDB, I noticed that although GDB said my threads exited, my main thread was still block at pthread_
- 1 Unresolved Followup
Sun

1
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trouble with vector

i push target names into a vector when they are done, and my code does increase vector size and does complete the push,
Sun

0
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Trying to get correct cycle detection

Does bool graph_adjacent(graph *this, void *s, void *t); Does this function return true if there is an edge between th
Sun

0
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will files and scheduling be tested?
Sun

1
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Quiz Scheduling Time (Anybody want to trade for an 8 pm slot?)

I have my quiz scheduled for 8 pm today but I realized I have a meeting at that time now. Would anyone be willing to swi
Sun

3
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Instr Autograder Lab Scheduler Feedback Error

Dear 241 Students, If you receive the following message in Scheduler AG feedback, it means the AG were not be able to f
- An instructor thinks this is a good note
Sun

5
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Autograder timeout

b: c d echo "This is B" sleep 2 c: e echo "This is C" sleep 2 d: e echo "This is D" slee
- 2 Unresolved Followups
Sun

0
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Terminating threads confusion

My basic structure is the following: 1. I generate a list of relevant nodes that we should look at by using a very simp
Sun

0
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Hard Test Output

The extra output explaining what went wrong doesn't appear on the latest autograder run. Instead, the only output I
- 4 Unresolved Followups

▾ Last week

Sat

0
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testfile4 with 3 threads approximate parallel time

Could someone tell me approximately how much time it took them to run testfile 4 with 3 threads?
- 1 Unresolved Followup
Sat

0
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data race with barrier

I'm trying to use barriers for parmake. However, TSAN reports a data race with pthread_barrier_init and pthread_barr
Sat

0
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Multi-threaded cycle detection

Is it acceptable to detect cycles with a helper dfs method inside the main function in a single threaded way before doin
Sat

2
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testfile 3 output

so i run ./parmake -f test_makefiles/testfile3 -j 1 and i get the output [Stage 1](#1): This should run as part of "
Sat

0
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RAM size of 64bit machine

From the wiki page: If a 32 bit machine has 2^32 (4GB) of RAM. ... It's unlikely that a 64 bit machine will ever ha
Sat

5
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Only tsan miss some outputs

My tsan doesn't report warnings, but I notice that the output of tsan always miss some outputs. For example when I
- 1 Unresolved Followup
Sat

0
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Confusion about plrtf

so what are we considering for this function total runtime or the remaining run time?
Sat

2
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set threadsafe

Is the provided set threadsafe?
Sat

7
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Usage of graph_set_vertex

Is this the correct usage of graph_set_vertex: graph_set_vertex_value(G, rule->target, rule); where G is the graph
Sat

1
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Instr Autograder Lab Scheduler scheduled

The AG for Lab Scheduler scheduled! Schedule: "2017-04-01 22:00", "2017-04-02 22:00", "2017-04-03
- An instructor thinks this is a good note
Sat

7
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Parmake Segfault conditions?

So, in part one of the autograder and throughout all of the testing using the local makefiles, my parmake did just fine.
- 1 Unresolved Followup
Sat

0
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Rule clarification

From the flowchart: Given a rule that is a file, "Does the rule depend on another rule that is not a file on disk?&#
Sat

2
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Why need char **run_targets in parser_parse_makefile()?

To make a graph, we need to use graph *parser_parse_makefile(const char *makeFileName, char **run_targets), I'm conf
Sat

2
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failed due to exec vs failed due to cycle

I went over this with a TA but I just want to be sure: Lets say we have all: a b c, and c is a cycle. Then neither a, no
Sat

3
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Got "Timeout T_T" for most test cases of part2

I passed part1 with full points. But I got most time out message without actual running time given for part2? Is that be
Sat

8
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"one bad printout" on hard test

I know a lot of people were having trouble with this test for this reason. Mine says to check to make sure everything is
- 1 Unresolved Followup
Fri

2
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Same threads?

do we need have to reuse the threads we have previously made or can we keep changing the number of threads to amount of
Fri

5
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queue.h details

If we destroy this queue what happens to all the threads waiting on it Also is there anyway to see if the queue is empty
Fri

9
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Order of target_names

I am confused on the order of the target in a makefile. For example, if I have such a makefile a: b c echo A b:
Fri

2
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Parmake part 2 thread exec

Hello, In need of a bit of clarification if possible. If you ran testfile4 with 3 threads, does it not matter the order
Fri

2
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When to check File Access Time

When should we check to see if a rule's file dependencies has a newer modification time? I can imagine a scenario w
Fri

9
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Hard test feedback clarification

If we get the response "Too few lines of output!" in the hard_test autograder, should I take that to mean that I
- 1 Unresolved Followup
Fri

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Conflict final exam

Hey do I request for conflict final?
Fri

4
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Speedup for parmake?

Using the time utility with the following inputs, I get the following outputs: (one thread) time ./parmake -j 1 -f test
Fri

2
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Parmake part 2 clarification

Hello, I noticed one of the two requirements that are on the doc: Does that mean the queue has to in an order wh
Fri

6
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Does order matter?

./parmake testfile2 B C A For example would this be right as well I changed my implementation and now instead of CBA i
Fri

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Using Condition Variables

This was mentioned in another post, but I'm confused: is it advisable to use condition variables? If not, how should
Fri

7
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What is the time complexity of graph_antineighbors()?

Is it O(1) or O(|V|)?
Fri

4
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How much would it affect my grade if I received an absence for two labs?

<code>Lab Attendance & other items: 4% </code> What are the other items?
Fri

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redo part 1?

I got 11/17 points for part 1. I was wondering if I need to fix my implementation for part1 in order to be eligible for
Thu

3
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Mutating rules in graph

Following what @2010 said, does the instructor response imply that the returned value from graph_get_vertex_value is
Thu

12
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How to stop (return) when queue is empty?

How do we stop working threads when queue is empty (after we complete all rules)? My codes just hang after completing a
Thu

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multithread sequence

If I have a makefile looks like this: A: x y echo A B: y z echo B x: echo X y: echo Y z: echo Z and running with c
Thu

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Thu

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what's meaning for busy wait for hard test

I didn't pass the cycle test of part one due to time out. Is this the reason for failing with hard test? (I passed
- 1 Unresolved Followup
Thu

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cycle detection test for part2

I got 2/3 for cycle test in part 1. Will testcases in part 2 test cycle again? If it is true it seems like I have to red
Thu

9
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How to Debug Parmake 'Hard Test'

I'm failing one of the hard tests for the parmake autograder with a bad printout, but it doesn't say which one.
- 2 Unresolved Followups
Thu

1
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Instr [SVN UP] scheduler

Please svn up in order to have a writable libscheduler.h so you can modify the job structs! Thank you CS241 staff
- An instructor thinks this is a good note
Thu

1
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Instr Scheduler scheduled

Hello everyone ! We have released the scheduler lab. This lab is located in your svn repo at: https://subversion.ews.
- An instructor thinks this is a good note
Thu

5
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Another chance for the pied_piper lab?

this lab was a good opportunity to learn about pipes, but it just took so long (for me) to understand everything require
Wed

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can't get into ssh server

channel 0: open failed: connect failed: Connection refusedstdio forwarding failedssh_exchange_identification: Connection
Wed

0
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print_failure_report(failure_information *info, size_t num);

Search through a few documents and still confused, what should num be?
Wed

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All I read from my pipe is garbage.

I got an pipes array. and I use dup2 to redirect pipes[0][1] to inputs <code> close(pipes[0][0]);dup2(input_fd, pi
Wed

2
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Weird Seg fault error

My print_failure_report is seg faulting for some weird reason. It seg faults at the point of qsort() Is my declaration a
Wed

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stderr "No Standard Error Output."

I'm detecting failures properly, but I just can't seem to get the output of stderr, I always get something like
Wed

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packet_write_wait

When I try to ssh, I got packet_write_wait: Connection to 172.22.153.30: Broken pipe How do I fix this?
Wed

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VM not working.

Me and my two buddies are all having trouble with the VM, we've been kicked out twice now.
Wed

4
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Instr Autograder MP Parallel Make Part 2 Released!

We have released Parallel Make Part 2 AG! Schedule: "2017-3-29 22:00", "2017-3-30 22:00", "2017-3-3
- An instructor thinks this is a good note
Wed

3
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input/output file examples

What are some examples of input and output files we use to test pied piper? Do we have the create them ourselves or are
Wed

2
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Content on Quiz this Week?

Can someone (instructor plz) explain the content of this week's quiz? I would love that so much.
Wed

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Exec doesn't work with ps

Hope this gets responded to before midnight.....anyway I print out the executable immediately before using exec_command(
- 1 Unresolved Followup
Wed

2
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Output not correct

I am getting a very weird error ./pied_piper -i hello.txt "sss" "ssd" Error: Invalid output file /bin/s
Wed

2
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Fail nth not catting

For some reason my fail nth program is not catting no matter what. Any reason for why this could be?
Wed

14
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Child not finishing

When I run sleep in the background and then do something like ./pied_piper "ps" "grep sleep" My ps prin
- 4 Unresolved Followups
Wed

1
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failing failure_test

I am failing failure_test. Here is the result when I test my program: cs241/NETID/pied_piper$ ./pied_piper -i test.txt &
Wed

3
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exit status 256 and 1

Are these synonymous somehow? I get an exit status of 256 if I cat an invalid file, and that status seems to stay 256 un
Wed

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restart test

I failed restart_test( Description: Test that processes are being restarted upon failing ) But I passed failure_test. Ar
Wed

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About invalid input_fd and output_fd.

I have read @2087, but I am still confused. I think I should use the provided function to print an error message and
Wed

2
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Pied Piper Failure Test

What exactly is the failure test testing? My output for commands and ./fail_nth look correct, error messages are being f
Wed

1
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does this output look correct? (testing question)

I am trying compare my output with the real pipe command. Does this look fine?
Wed

9
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Desperate about Failure Test?!

So, I've done all I can think of, yet I still don't pass failure test. I have tested my Pied Piper with a custo
- 2 Unresolved Followups
Wed

1
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Lab AG

Screen_Shot_20170329_at_6.39.03_PM.png what does this output mean..?
Wed

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if one command failed, should other still print to stdout

here should echo "happy"???
Wed

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test output

./pied_piper "./fail_nth out.txt 3" "./fail_nth o.txt 2" -1-1Command "./fail_nth o.txt 2" exite
Wed

6
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Pied Piper Negative one at start

Sometimes when I run pied_piper, I get a -1 at the start of my output file. Is this a problem? Or does anybody know why
Wed

0
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Instr PP: Failure Information Clarification

Dear CS 241 Students, When creating the failure information structs, you need to save all of status (as returned by wai
Wed

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wondering is this normal?
Wed

2
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extra newline after error printing

My error prints show up like this: Is this normal?
Wed

3
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piping stderr

I'm really confused on how to do this. Right now I set up a pipe in the parent process, then in the child process, i
Wed

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How to fork before waiting for children without fork bombing

Currently, I had a for loop that did for(int i = 0; i < numCommands; i++) {
Wed

2
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get error message

I am confused about how to get stderr outputs from child processes. Do I need to set up extra pipes to get error message
Wed

4
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How to assign pipe in child process

I have created n pipes for n commands, and write a exec function to fork all the n processes at the beginning and execut
Wed

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How do we test this program using failure nth?

-
Wed

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Difference between failure test and restart test?

Somehow, I passed failure test but managed to fail restart test? How is this even possible? Restart test says "Test
- 1 Unresolved Followup
Wed

2
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fdopen segfault

FILE* reader[i] = fdopen(error[i][0], "r"); I try to do this line to open the read end of the pipe, but it retur
Wed

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Failure test

I honestly don't know what else to do lol. My code returns a non zero number if exec_command fails. If any process f
Wed

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Weights of MP's in gradebook

Are all of the one week MPs (i.e. Shell, Vector) worth the same amount of our total grade (about 3.8% as shown in the gr
Wed

4
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when and how do I flush each pipe?

When I run pied_piper with two commands, it seems like only the first command runs and then the program stalls. I think
Wed

4
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How to deal with SIGPIPE

Supposed that there are 3 processes running parallel, the second process doesn't need the first process's output
Wed

3
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memory error in print failure report

==18633== Conditional jump or move depends on uninitialised value(s) ==18633== at 0x400C93: print_failure_report (in
Wed

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waiting for children

I'm a little confused on the documentation, do we wait for each child before starting another process or do we go th
Wed

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No output

I'm running a very basic test with no errors. It greps for a statement in the input file, and cats to an output file
- 1 Unresolved Followup
Wed

4
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Instr PP AG: Invalid Command Test Dropped

Dear CS 241 Students, All subsequent autograder runs for pied piper will not have the invalid command test. There is a
- An instructor thinks this is a good note
Wed

2
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print failure report format

Do we need to strip the redundant '\n' at the end of stderr when printing failed command
Wed

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SIGPIPE

Processes receive the signal SIGPIPE when no process is listening! From the pipe(2) man page - <code>If all file d
- 1 Unresolved Followup
Wed

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why closing pipe before wait?

My child process seems not terminating either way. Any suggestions?
Wed

5
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Instr Moving my office hr

Hi all, This is Wei-Chun. Sorry that I miss this mornings office hr. To make up, I'll hold an office hr on Friday m
Wed

3
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Office Hours Today?

So 9 AM's office hours today got mysteriously removed from the calendar, and now I don't see the TA for 10 AM
Wed

3
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How to test

I've seen other posts talking about using some input file, but I'm confused on what this file should be, or how
Wed

12
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What does error_message refer to in utils.c?

Any examples on error_message? Thanks in advance!
- 1 Unresolved Followup
Wed

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Non zero return code

According to the doc, If any process has a non-zero return code, then restart the script (go back to step 2). What doe
- 1 Unresolved Followup
Wed

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fail_nth, nothing in executables?

I've been trying this on my pied_piper ./pied_piper -i test.txt "./fail_nth output.txt 3" the way that I'
- 1 Unresolved Followup
Wed

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Problems using awk as a command argument

I am testing to see if my pipes are hooked up correctly, but for some reason, the awk command doesn't seem to work a
- An instructor thinks this is a good question
Wed

3
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lost in the lab

call me dumb, but reading the piazza posts and the lab page did not really clarify me of my questions: 1. so what if of
Tue

4
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Failure_test? Also, good input?

Does failure_test only test to make sure you only run the script at most three times? Because right now, with my current
Tue

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Speediest Question Ever

Is this correct output? $ ./parmake -j 1 all ./Makefile:1: *** missing separator. Stop. trying to make sure there is no
Tue

2
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Final run processes

Hi, according to the documents, when it is not yet the final run and a process fails, we restart the script (back to ste
Tue

3
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invalid command

If exec failed due to an invalid command, should the parent exit immediately or after three tries?
Tue

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Instructor Responses on Pied Piper?

From my observation, it seems like very few questions asked about Pied Piper on Piazza are being answered, and I've
Tue

6
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Wait/Exec freeze

Whenever I try to use wait() or waitpid() in a loop to catch the child processes, the second wait always freezes, regard
- 1 Unresolved Followup
Tue

0
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missing separator

What does missing separator mean? Am I somehow forgetting the null terminator in targets?
Tue

2
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failure printing

when printing out the failure information, do we print on every run when there is a failure or just the last run (if it
Tue

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rule struct labeling

I'm trying to implement the cycle detector by using dfs function. But I am confused about what to do with the rule_t
- 1 Unresolved Followup
Tue

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testfile8 contradiction

Testfile 8 seems to contradicts itself and the most recent post by Nav. all: a c echo This command should not r
Tue

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Can I just say how awesome you all are?

:)
Tue

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What should the output be?

A:B B:C C:B what should this output if I run make by itself.
Tue

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Pied piper invalid_command_test

Anyone else failing this test case? It seems to me that the test is sending invalid executable, but i think i handle tha
- 1 Unresolved Followup
Tue

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output questions for ./parmake testfile10 all (Last Clarification)

Should you run all a, b and c in this case when there's is no cycle with allAlso,In the case where there is a cycle
Tue

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invalid use of defined type 'struct vector'

I'm making a new post because my last one will likely be buried and remain unanswered. When I try to make parmake I
- 3 Unresolved Followups
Tue

7
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What should this print? when you run ./parmake -f testfiles/testfile10 with no build targets

all: a b c echo "This should not display" a: all echo "this shoud not display" b: echo "HIIII
Tue

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What should you print if you run ./parmake -f test_makefiles/testfile8 all

<strong>Shouldn't it run all and print the echo command from c and drop the build target all?</strong>
Tue

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stderr from child process

I'm having trouble getting the stderr output from the child processes. I'm piping the child's stdout to the
Tue

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Instr Dependency Failure Clarification

Hello everyone, Since many students are still failing the fail_dependency_command_test test, let me clarify something m
- 2 Unresolved Followups
Tue

3
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questions about fail_dependency_command_test

I kept failing this case and I don't know why. I passed the test case in test_files and the test cases I wrote my se
Tue

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Trouble with the cycle test

It seems I am receiving 2/3 on my cycle_test with the autograder. The output reads: Trying to compile your code... Succ
Tue

2
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In pied_piper, we need to parse the command line to get the argv right?

Since each *execuatables is a command with arguments <code>"command1 [args ...]"</code> we need to p
Tue

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am I getting the gist of this lab?

Correct me if I'm wrong. We're supposed to pipe each executable and throw each one into a process. and then wait
- 1 Unresolved Followup
Tue

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Getting a 0/3 on cycle test and 0/2 on dependencies

I've exhausted several test cases, including ones on the Piazza, and my results are accurate for every single one, b
- 3 Unresolved Followups
Tue

4
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touch test

i am still failing the test case using int a = stat(..); int b = stat(...);if difftime(curr_buff.st_mtime, dep_buff.st_
- 1 Unresolved Followup
Tue

2
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Output?

a: b c echo A b: c echo B c: echo C What should be the output if I type ./parmake -f test_makefiles/testfile2 -j 1 a
Tue

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Sibling dependencies

Does all the sibling dependencies need to be worked on if there is cycle dependency on this rule?
- 1 Unresolved Followup
Tue

2
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Required exec wait pattern?

Currently in my implementation, I have a single pipe and I go through each command, one by one, and exec them in order,
Tue

2
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Not sure why fail_dependency_command fails..

I am passing testfile7 and even made new makefiles. Is it perhaps what I use to check if a command has failed is: if(WE
Tue

2
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Pipe blocking?

So, if you have a pipe open between two processes, and one expects input from STDIN, but the other never writes to STDOU
Tue

0
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Failed commands write to file

If I run the following command, assuming files are valid ./pied_piper -i input_file -o output_file "./fail_nth temp
Tue

4
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Error reading?

So, for Pied Piper, I am trying to figure out how to get errors printed from all of the commends executed if the final t
Tue

0
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Several questions about pied_piper

When I doing the lab, I have following questions: 1. Error format: Should we keep the new line in stderr or convert it
Tue

2
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capturing output to stderr

I get that we can do this using dup2 to some kind of buffer, but won't that just give us a long string with no way o
Tue

9
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Assigning const char *error_message;

I am not sure how to go about this. I assigned all the other elements of the failure_information structs but I can't
Tue

0
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target orders

When we run the makefile with targets, does the order of the targets matter? For example, if I have such a testfile a: b
- 1 Unresolved Followup
Tue

2
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Lost in the lab

Here is what I am trying to do. Let's say we have 3 commands to execute, I have to fork for three times and set up 2
Tue

0
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unsure test results

Screen_Shot_20170328_at_16.25.22.png should the output for this be the fail command and "C" and "E" or j
Tue

0
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touch_test timeout

I passed the local testfile5 and keep getting timeout in AG's touch_test. What could be the reason of the timeout?
- 1 Unresolved Followup
Tue

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How to find the first target in the makefile

So in format.h, it says: This function should * only be called on build targets, i.e. the positional arguments to make
Tue

4
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cycle test (1/3) time out

I tried all the examples on piazza and also tried many complex cycle and my cycle detection worked fine with all of them
- 1 Unresolved Followup
Tue

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Failing Invalid Command Test

I'm failing the invalid command test for the Pied Piper lab. Which part of the documentation describes how to handle
Tue

0
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Cycle output example

Given a makefile: all: a c echo Aa: b echo Bb: a echo Cc: echo D If parmake is given the build targets, ./parmake -f fi
- 1 Unresolved Followup
Tue

1
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Instr Autograder Lab Pied Piper is Back Online

Dear 241 Students, We have restarted AG for Pied Piper. An additional run ("2017-03-29 18:00") has been added
Tue

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print order matter for output?

Lets say I have a cycle in my graph, but node C can be run okay since its not dependent on the cycle, but node A is depe
Tue

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confusion about failure_information and num

for function: void print_failure_report(failure_information *info, size_t num); I understood that failure_information-
Tue

2
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fail nth not working?

I made an input file which contained some text and tried to run fail_nth by itself: ./fail_nth input_file 3 But it does
Tue

2
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Print stderr

I know that if the third try fails, we need to print out the stderr message. For example, there are five commands needed
Tue

5
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exec_command freezes

I am trying to test pied_piper with this simple command: ./pied_piper -i hello.txt -o out.txt "grep hello" "
- 1 Unresolved Followup
Tue

2
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Handling bad input/output fds

In pied_piper.h there are defines for EXIT_BAD_INPUT and EXIT_BAD_OUTPUT. In the docs it says that If either the input
Tue

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Instr office hours cancelled today

Hello, i'm not feeling well and lost my voice this morning.. due to this I'm cancelling office hours today 6-8pm
Tue

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Getting a 1?!

I am seriously unhappy about this. I spent so much time on this MP yesterday and all I got was a 1. What could possibly
Tue

5
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nvm

.
Tue

2
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Cycle test?

Do you print that "all" have a problem or "all, a, and b" have a problem...when printing output message?
Tue

5
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Lost on rules

At first from the docs and other posts I thought rules and files were essentially the same—that is, a rule is a set of t
Tue

1
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Instr Reducing my OH on Tuesday 03/28

Hi, I'll be having my OH from 8-10 instead of 8-11, since I have to attend a seminar from 10-11. Sorry for the lat
Tue

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graph get neighbours

Does this function return all the nodes that are adjacent or does it exclude it's parent?
Mon

3
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Question about the failure print of the pied_piper

At the last round, what are we supposed to print? If we detected a error in any child processes, should we stop immediat
- An instructor thinks this is a good question
- 1 Unresolved Followup
Mon

15
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Instr Autograder Lab Pied Piper

Dear 241 Students, The AG for Lab Pied Piper ran into an unexpected error. We are looking into it. The AG will be rest
Mon

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Instr Autograder MP Parallel Make Part 1 Schedule Updated

We have added more additional runs for MP Parallel Make Part 1. "2017-03-28 00:00", "2017-03-28 14:00"
Mon

2
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exec problems

For the pied_piper lab, are we supposed to use the exec_command provided for us in utils.h instead of the exec() to exec
Mon

3
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Invalid use of undefined type

I'm trying to get a rule_t pointer using graph_get_vertex_value and typecasting as a rule_t *. Doing that gives me t
- 1 Unresolved Followup
Mon

0
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Instr DEADLINE EXTENDED - Parallel_make pt1

Hello everyone, We have decided to extend the deadline for parallel_make MP to March 28th, 11:59PM. This gives you extr
- An instructor thinks this is a good note
Mon

2
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rules and graph

if i modify the status value of my rule, will this change be reflected in my graph as well?
Mon

4
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question on lab

For the initial file that we are reading from, Are we allowed to just use getline() and write those contents to the pipe
Mon

0
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I am not sure why this gets me a segfault

I made a helper function that takes a rule_t* as a parameter. To use that function, I created a 'rule_t ** rules
Mon

0
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Testfile8

I have a major problem in testfile 8, when I get the vertices into a vector the empty string is at position 1, but for o
Mon

0
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parsing error

./test_makefiles/testfile9:5: *** missing separator. Stop. when I made my own testcases, sometimes I got the above erro
Mon

6
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Cycle test

I got a 0/3 on my cycle test even though It works perfectly for test 8 (right outputs) and i've tested it out on a f
Mon

2
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Dictionary.h too many arguments

I don't know why I got a compilation error on autograder, while it compiles correctly on my vm. FYI, I am currently
Mon

7
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lost on dependencies test.

I passed all other tests except this one. I even have tried to write many custom tests and it seemed that I passed all o
Mon

3
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print_failure_report printing correctly only sometimes

I'm running /pied_piper -i input.txt "./fail_nth output.txt 7" where input.txt just has random stuff to cat
Mon

3
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build targets recursively

I managed to check the makefile/Makefile command but i'm not sure what are we supposed to do with build targets? Are
Mon

7
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fail output order

I failed basic_test1 and target_test (1/2) and it gives me the following output: basic_test1: Trying to compile your cod
- 3 Unresolved Followups
Mon

2
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Conversion between sockaddr_in and sockaddr

Hello, In the wiki book, we are provided with the code that builds up a TCP server. https://github.com/angrave
Mon

2
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what is supposed to be the correct output when i run testfile8 without any targets

./parmake -f test_makefiles/testfile8 -j 1
Mon

4
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My grade report hasn't updated since before the spring break?

Any idea why that might be the case?
Mon

5
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time granularity clarification

According to the docs, "to determine whether a file is NEWER, you should use stat and difftime to determine if it is
Mon

5
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print_cycle_failure clarification

I just wanted to clarify what the expected output for testfile8 should be if this command is run: ./parmake -f test_mak
- 1 Unresolved Followup
Mon

5
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Cycles

If we have a triangle like cycle should we print out all the vertices involved? Or just the neighbor of "" (assu
Mon

1
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system() return value

I'm trying to check for failure. The man pages say that it returns -1 on error. I wrote my own test case with an inc
Mon

2
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Touch fail?

So, on the auto grade before break, I was passing the "touch test" just fine, and locally when I test makefile8
Mon

15
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Cycle_test(1/3)

I have passed all the test except the cycle_test. I have read all the post that have similar problems, but I cannot find
- 1 Unresolved Followup
Mon

3
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failed dependency vs cycle

Hi, According to the specs: If a rule fails, its parent rules (rules which have this rule as a dependency) should fail
Mon

6
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Print invalid files

Do we need to use the print_invalid_input and print_invalid_output functions if input and output fds are negative?
Mon

17
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Parmake autograder

I passes every testfile except testfile8, however the AG only passed the basic_test2_slow and the memory test. Any thoug
- 2 Unresolved Followups
Mon

10
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Cycle Test AG Timeout

I am getting a 0/3 on the cycle test on the ag and it says my program is timing out. But when I test using testfile8 I s
- 5 Unresolved Followups
Mon

5
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Error printing?

So, if we have a following command structure: IN->a->b->c->d->e->OUT And then "c" fails ever
- 1 Unresolved Followup
Mon

0
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fail nth usage

I see that we're supposed to use fail_nth usage like ./fail_nth [file] [num_times], but how do we use it in conjunct
Mon

3
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freeing failure_information

When I create a failure_information, I first need to malloc a buffer which i use to pipe stderr. I then set the failure
Mon

1
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valgrind memory allocated

I do not get any errors when I run tsan but if I run valgrind on the test cases I get that different number of bytes wer
Mon

5
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set_contains

I have problem with set_contains. I create a set stack with stack = set_create(char_hash_function, char_compare, char_co
Mon

0
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dictionary usage

I'm trying to use the provided dictionary structure (string -> int). But for some reason when I use contains() it
Mon

0
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Prehistoric Queue

The Chara queue up right now has existed since the Friday before break; will it be deleted before the first office hours
Mon

7
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Dep_fails

I wrote a test case for dependency failed and I was wondering if the last line should be displayed? a: b d echo
Mon

0
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GitHub Pages is temporarily down for maintenance.

I couldn't open the lab and the MP page for the 241 website :( When are we able to see them again
Mon

2
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testfile5 does not create examples/file1

When I tried to run ./parmake -f test_makefiles/testfile5 It did not create file1 in ./examples repository. However, it
Mon

5
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0 bytes after a block of size 1 alloc'd

When I test my code with targets like this ./parmake -f test_makefiles/testfile2 c It worked as expected. But when I ran
Mon

0
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questions about "data" in rule_t struct

1. Is it possible to solve the MP without using the "void* data" in the structure? (I know it would help if we u
Sun

0
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Touch Test difftime

When we call difftime on the two files we are supposed to call difftime on the last modified times correct?
Sun

0
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Execute targets that have been executed before

Say I have a makefile like this a: b c echo A b: c echo B c: echo C If I run that file with target a c, should I get
Sun

0
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Practice Midterm 2

Is it possible for us to have a practice midterm 2 just like we had for 1? If so, can we have it during the week or some
Sun

2
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Cycle Detection AG Timeout? (2/3)

I've read about some other people having trouble with this, but haven't found any solution that has been able to
- An instructor thinks this is a good question
Sun

3
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file test

How many of the AG tests rely on the file_test (test_file 5)?
Sun

0
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Is it right & efficient to do this with rule_t?

So I am planning to make rule_t for each target in the makefile. For example, for such makefile that looks like: a: b
Sun

2
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why did you guys give us a queue?

I don't see how a queue would help. am i missing something?
Sun

4
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difference between graph_contains_edge and graph_adjacent

/** * Returns whether the graph contains an edge between two vertices whose * representations are 'key1' and &
Sun

2
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Make targets order wrong

Hello, I am confused about the running order of the targets. I wrote up a makefile that have rule a b c d where
Sun

2
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rules

rule=target+dependency+command or rule=target+dependency?
Sun

2
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testfile8

The testfile suggests that command C should get run if and only if we run: ./parmake -f testfiles/testfile8 c but someon
Sun

4
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graph assert ?

I assigned the target a,b, and c and made sure if they are successfully assigned to the target array by printing out l
- 1 Unresolved Followup
Sun

4
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default target

On the documentation page, it says, The list of targets will always come last and is optional. If no targets are listed
Sun

4
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part1 autograder

do we have to pass all provided test cases to get points? Also, for part1, can we just test with no thread options (1 t
Sun

2
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how to use gdb in parmake?

I got "value has been optimized out" error.
Sun

0
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dup2 for stdin and stdout

To continuously redirect the stdin and stdout file descriptors for child processes, do we have to continuously dup2 to s
Sun

2
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Error message from stderr

Hello, In the doc, it is required to print out the stderr message of each executables if the third try fails. I
Sun

2
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Graph Concurrent Reads

Even though the graph class is not thread safe, can we perform concurrent reads from the graph structure (ie, graph_get_
Sun

4
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clarification on files on disks

I'm a little bit unclear about the flow chart. I check if each rule is a file on the disk. If it is, then I check
- 1 Unresolved Followup
Sun

0
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Does print_failure_report() print to the output file? (NVM, resolved)

I am redirecting stdout to pipes as I'm expected to do. But it turns out that every time I call print_failure_report
Sun

7
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Removing a target and state

How do we "remove" a target? Do we just use graph_remove_vertex? Will this disconnect all adjacent nodes in the
Sun

0
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does graph_vertices include sentinel node?

I tried to print out all vertices in the graph by using the function but the very first index returns an empty value li

▾ Week 3/19 - 3/25

3/25/17

5
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lost in the MP

Here's what I have so far. I parsed the appropriate information depending on the arguments. For example, ./parma
3/25/17

4
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How to use a dictionary across threads?

I keep getting this problem in some form: ==28272== Invalid free() / delete / delete[] / realloc()
3/25/17

2
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makefile order (visual question)

d: a c echo D a: b echo A b: #a (comment out 'a': no more cycles if you remove this edge!) echo B c: echo C
3/25/17

4
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sentinel node

in my previous question about sentinel node, i asked about the role of the sentinel node, and got an answer The senti
3/25/17

2
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Input file is output file

When I run ./pied_piper -i test.txt -o output.txt "cat" "wc" I got the following error: cat: -: input fi
- 1 Unresolved Followup
3/25/17

3
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Depth first search

I'm running a DFS on my graph, when I run the function and put print statements in the function, the state of each r
- 1 Unresolved Followup
3/25/17

2
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Understanding cycles.
3/25/17

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cycle detection

I have passed all the given testfiles but I still have a question. For the following makefile what should be the correct
3/25/17

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Second chance for MPs

Will we have a chance to re-submit past MPs to improve our grades on them, as was offered in previous semesters? Please
3/25/17

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char **executables

In int pied_piper(int input_fd, int output_fd, char **executables) function, executables doesn't include the input f
3/25/17

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cycle_detection format

For test 8, if we ran "./make a b c" should that just print out cycle_failure("a"), cycle_failure("b
3/25/17

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Compiler issue with Format.h

Has anyone gotten this issue? I haven't modified format.h or format.c.
3/25/17

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How to find where an assert failed?

I feel like I am close to having my parmake fully parallel, it seems to work on the example makefiles, except when the n
- 1 Unresolved Followup
3/25/17

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clarification with invalid makefile

<code>parmake [ -f makefile ] [ -j threads ] [ targets ] </code> If a -f makefile is not specified, ./mak
3/25/17

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signal handler after exec

Hello, I am trying to catch the SIGPIPE in the child process that invokes exec. Am I be able to use the regul
3/25/17

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system() question

The documentation page states, "You can use system() to run the commands associated with each rule. There are a fe
3/25/17

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parser_parse_makefile question

I have three questions to ask about the function. 1. According to the documentation of parser_parse_makefile function,
3/24/17

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Cycle Detection

I created a helper function that looks through the dependencies to see if there are any cycles and when I am testing it
3/24/17

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graph_get_vertex_value

rule_t * rule = (rule_t *)graph_get_vertex_value(dependency_graph, target_name) I am not sure how the command above giv
3/24/17

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print_failure_report docs clarification

The pied piper docs specify: 6. If not, print out a summary of commands, their return codes, and anything printed out to
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3/24/17

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resource allocation graph question

On the wiki page, it says If there is a cycle in the Resource Allocation Graph and each resource in the cycle provides
- An instructor thinks this is a good question
3/24/17

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Creating a vector of rules

II was creating a vector of rules and tried to use the init, destroy, and soft copy function given to us, but those func
3/24/17

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Do we execute in parallel?

For the lab do we want to execute the commands in parallel since we always want a want a process listening on the pipe o
3/24/17

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Circular Depedency

For testfile 8. If we run "./parmake -f testfiles/testfile8 all" should we print: 1) print_cycle_failure (&
3/24/17

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tsan-valgrind

I do not have any memory leaks but when I run valgrind on my parmake I allocate about 144,323 bytes on test case 4, is t
3/24/17

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no idle thread

Since the mp requires the thread should not stay idle when there are jobs that can be executed. Then I guess the progra
3/24/17

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clarification with testing pied_piper + additional questions

In order to run something like ls | grep -v vim with our pied_piper, do we have to do something like ./pied_piper &#
- 1 Unresolved Followup
3/23/17

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Are we allowed to open a new file for the lab?

Hello, I am wondering that if we are allowed to open another file to record the output of each program before p
3/23/17

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Instr Autograder MP Parallel Make Part 1 Additional Run

Dear 241 students, As requested by some of you, we will add an additional run for MP Parallel Make Part 1 on Monday 6:0
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3/23/17

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FDs and Pipes

So when you are forking, and the parent is doing all the writing and the child is doing all the reading, the professor m
3/23/17

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pied piper idea

For pied_piper, I know that the char** executables parameter works something like argv, and each char * will be a strin
3/23/17

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multi-thread

I am working on the multi-thread part and when I run it I get a segfault. If I put a usleep(rand()%50000) in the thre
3/23/17

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Can two rules be in a target? Confused with this.

rule3 rule4: finalcommand
3/23/17

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print_failure_report size_t num

what is the num argument used for in print_failure_report?
3/22/17

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graph_set_vertex_value(graph *this, void *key, void *value)

I would like to know if the type of key is rule_t* or char*(just the node target)? And can i use this function to chang
3/22/17

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proper cycle handling

If there is a cycle between two build targets, do we remove both of them or just one?
3/22/17

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AG run

Some of us were really busy during the week before spring break with other midterms/interviews/travel and such and didn&
3/22/17

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graph_neighbors

vector *graph_neighbors(graph *this, void *s);does graph_neighbors return all vertices that s points to only? or all ver
3/22/17

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cycle detection

the MP page says that we should announce any dropped build targets due to cycles before working on any rules. does that
3/22/17

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Number of Failure Info Structs

Do we need one failure_information struct per process, or only one per failed process? Just from reading the code in uti
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3/22/17

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Quiz 4 contents?

As the title.
3/22/17

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file shared between processes

Hello, In order to check if change position of a file using fseek in parent process can impact the shared fi
3/22/17

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pied piper parameter

I am confused with the given parameters of the pied_piper function (int input_fd and int output_fd) Usually when we cre
3/22/17

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Confusion between files vs. rules

I'm a bit confused on the dependencies. So the dependencies can be either rules themselves or files, or both. So the
3/21/17

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Compiler Error on "graph_contains_edge"

$makegcc .objs/parmake-release.o .objs/parser-release.o .objs/rule-release.o .objs/parmake_main-release.o .objs/format-r
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3/21/17

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piper lab question

Just to clarify, on the implementation instruction it says, The pied_piper() routine is passed two file descriptors, o
3/20/17

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How to get the modification time of a file ?

How to get the modification time of a file and How to determine whether a target is a filename in the disk or not? Can a
3/20/17

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What does the "sh: x: not found" stand for?

@sp17-cs241-188:~/cs241/parallel_make$ ./parmake -f test_makefiles/testfile1sh: 1: a: not found@sp17-cs241-188:~
3/20/17

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Reading and writing to pipes with executables

Usually with pipes, it seems its general practice to use read at one end and write at the other. In our case, can we ass
3/19/17

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Mysterious time out in AG

Does anyone come across the strange time out in AG "cycle test"? I passed local test8. Here is some output from
3/19/17

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failed with cycle detection

I thought my cycle detection will work but my AG failed. for the cycle detection I compared its dependencies and all its
3/19/17

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Flowchart Rule Dependency

I was looking at the flowchart ot understand how we want to go through the makefile and do the commands. I saw this p
3/19/17

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Invalid reads using the element returned from the vector

When I get a rule back from the vector I can read the target of the rule just fine using (char*)rule But when I try to
3/19/17

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Spring break office hours

Is the calendar up to date for over spring break? I don't want to go into school to find out that an office hour is
3/19/17

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forming a pipe with an existing fd

If I assign fd[0] = input_fd, when I form a pipe, will the pipes input fd remain the input for the pipe, or could that f
3/19/17

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Compiling error

Hello, I have this line of code in my parmake.c vector* adjacent = graph_neighbors(neighbor,entry); where neig
3/19/17

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touch test

I'm currently failing just the touch test, and trying to figure out why. My logic is this: 1. Check if the target we
3/19/17

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print_failure_information

Is the print_failure_information function something we should use in pied_piper.c? I don't understand where to get
3/19/17

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Is data structure 'set' thread-safe?

Is set thread-safe? I can't find the answer from document and .h file. Thanks for answering.
3/19/17

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What are the values of a key in the dictionary in graph?

/** * Sets the value associated with the vertex 'key' in 'this' to 'value'. * * If the vertex, &
3/19/17

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cycle_test (2/3)

I've written my own makefiles and made all permutations of cycles and independent build targets that I can think of.

▾ Week 3/12 - 3/18

3/18/17

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Test cases changed/updated?

I was getting a 2/3 on the cycle_test, but now i have a 0/3. Was the test case changed?
3/18/17

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Failing Touch Test

I seem to be failing the touch test on the autograder even though my program executes example makefile 5 correctly. The
3/18/17

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Malformed Graph Vertex Values

I have the following code for a graph g where key is a key in the graph: graph_set_vertex_value(g, key, "0");pr
3/18/17

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Exiting Parmake vs Returning on Error

In the argument parsing section of the docs, it says we should "Return a non-zero value if..." we cannot read/op
3/18/17

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For multiple targets, should we run one target twice?

For example: a: b echo Ab: c echo Bc: echo C When I do "make a c". Should target 'c' run twice? If '
3/17/17

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Does the order of targets matter?

If I have a test make file like: b: echo bc: echo c And I run: ./parmake -f testfile b cbc./parmake -f testfile c bb
3/17/17

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If one of the targets depends on another target, should we run both of them?

d: e echo "this is D"e: echo "this is E" Here, if my targets are 'd' and 'e', should i r
3/17/17

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Command line parsing

Hello, I am wondering that in order to parse the command line parmake [ -f makefile ] [ -j threads ] [ target
3/17/17

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test 5

all: examples/file1 echo "This (and the following lines) line should always be shown." echo
3/17/17

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dependency confusion

nevermind: misread
3/17/17

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Instr Autograder Lab Pied Piper (Rattenfänger von Hameln/ 花衣魔笛手) Released!

We have released Pied Piper AG! Schedule: "2017-03-18 22:00", "2017-03-19 22:00", ======== []ヽ(ﾟ
- An instructor thinks this is a good note
3/17/17

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ssh out of campus

so I'm going out of campus for spring break, but is it possible to ssh into your vm when you are out of campus? if n
3/17/17

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About the execution sequence of "same level" target

a: b c d e echo "[Stage 3]: This should be the last to run." b: d e echo "[Stage 2](#1): This should run a
3/17/17

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vector from graph has something wrong

I get a vector by graph_neighbor. Then I manipulate with this vector to do a modified BFS. It messes up. After I create
- 1 Unresolved Followup
3/16/17

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fail_dependency_command_test

"Description: Test that all parent dependencies stop when child dependency commands fail" I am faling this test
- 1 Unresolved Followup
3/16/17

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Instr [SVN UP] for Parallel Make

Hello, Please note that queue.h (again...) has included some nonthread safe functions you should not be calling. These
- An instructor thinks this is a good note
3/16/17

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stderr pipe

For printing the stderr of the last run of the pipeline, is there an easy way to get the current number of bytes in a pi
3/16/17

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fork failed

what if fork failed do we exit the program completely with nonnegative status or restart the script
3/16/17

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Modification time clearification

Documentation: "The rule is the name of a file on disk, and it depends on another file with a NEWER modification tim
3/16/17

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Question on fail_dependency_command_test

According to the description, all of the dependencies of a parent node should fail IF one such dependency fails to execu
3/16/17

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LIFO not FIFO?

I'm pretty confused as to why we have a queue instead of a stack to implement parmake. As we find dependencies for c
3/16/17

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Instr dup2 (CS241, pied_piper)

We have released the Pied Piper lab. This lab is located in your svn repo at: https://subversion.ews.illinois.edu/svn/
- An instructor thinks this is a good note
3/15/17

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Same VPNS Diff Offset

I've looked over my code and I'm not really sure why im failing the assertion 'frame == physical_address_dec
3/15/17

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mmu_test confirmation

Just to confirm, For the provided test cases, are we good if we the test prints out successfully without any assertion
3/15/17

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How many misses for multiprocess

Are we supposed to flush the TLB every time a new process is working, and if so, does that mean that if "Process A&#
3/15/17

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Maximum page faults possible

So if a process doesn't exist in mmu, then we: 1. MMU_add_process() (page fault #1 because base page table was creat
3/15/17

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Instr Autograder Rerun for Password Cracker

Hello, We have decided to make slight modifications for password cracker autograder tests, and reran the autograder ear
- An instructor thinks this is a good note
3/15/17

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graph function clarification

Since it is a directed graph I am wondering if when we use graph_remove_vertex(); does it also delete the edges that we
3/15/17

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Physical Address bits

So the physical address returned by ask_kernel_for_frame() should be a 64 bit address with the least significant 49 bits
3/15/17

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Difference between "target" and "rule name".

Hi, everyone. I am confused by the difference between "target" and "rule name". For example: (this is f
3/15/17

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mmu_test

what are these test outputs supposed to be? If i don't get any assert errors then it's good right?
3/15/17

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testing

im kinda confuse on how big or small the input number should be... And do we reference our result to the simulator file?
3/15/17

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C String Hashing Functions

For those of us who want to use the given set to hold strings, I found some easy-to-implement hash functions for C strin
- An instructor thinks this is a good note
3/15/17

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Failing Multiprocess test

I am passing the test when runned locally but failed the AG test. My code checks if the mmu-->curr_pid is the same as
3/15/17

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Page table entries

I'm having trouble understanding this part of the wikibook:"For a 32 bit machine with 4KB pages, each entry need
3/15/17

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64 bit machine ram

A frame is the same number of bytes as a virtual page. If a 32 bit machine has 2^32 (4GB) of RAM, then there will be th
3/15/17

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Build targets with shared dependencies

Suppose we have a makefile like this: a : x y echo Ab : y z echo Bx : echo Xy : echo Yz : echo Z and then we call make
3/15/17

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Helpful Videos for Virtual Memory

I found a series of videos quite helpful for virtual memory and wanted to share with your guys. Personally, I think it i
- An instructor thinks this is a good note
3/15/17

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TLB_add_physical_address (TLB **head, void *key, void *value);

What's the value in this case? the pid?
3/15/17

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FYI the 2PM Lab autograder is up fam

Has been up since 3:30 actually. That was fast! :)
3/15/17

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TLB_get_physical_address

When we get the physical address from tlb, do we need to add offset to it too?
3/15/17

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Setting entry

The way I understand it, if the first level page table returns a null for the index we want, we raise a page fault, crea
3/15/17

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If page table one wasn't created before can you assume page table two and three weren't either?

If Page_table_getentry(base,VPN1) returns a Null pointer do you have to keep checking to see if Page two and Page three
3/15/17

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How to access information in "Sentinel vertices"

Hi everyone. Does anyone know how to get the targets I want to make from the graph? I search for the document and found
3/15/17

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how is graph function using memory?

So I believe graph is on heap and the vector it returns is also on heap, and I have two more question. rule_t * rule = (
3/15/17

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Using graph_set_vertex_value and graph_get_vertex_value

I'm having trouble using the graph_set_vertex_value and graph_get_vertex_value methods. I have this following code:
3/15/17

2
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Instr Cancelling Friday Office Hours

Hi all, I have to cancel my 11-12 office hours this Friday (3/17). Sorry for any inconvenience this causes. Brian
3/15/17

5
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fork if curr_pid != pid?

I noticed that there was a question on an earlier post about forking and I was wondering if that is required for the lab
3/15/17

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.

never mind
3/15/17

0
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graph_antineighbor not found

After getting the newest graph.h from svn, I tried to use it as follow: vector* anti_neighbors = graph_antineighbors(g,
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3/15/17

2
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Pid

Do we need to update the Pid in our mmu if the passed in pid in our MMU_get_physical_address is not the same as the pid
3/15/17

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TLB Get Physical address parameter key. TLB_get_physical_address(TLB **head, void *key);

-
3/14/17

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Failing test_multiprocess

I am passing every test case except for test_multiprocess right now. I know the test cases provided to us aren't com
3/14/17

1
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AG doesn't have set.h

Could you rerun the AG? <code>Trying to compile your code... FAILED TO COMPILE! parmake.c:12:17: fatal error: set
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3/14/17

4
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graph_add_vertex is broken

It will cause a segmentation fault. Should I use graph_set_vertex_value instead, like the way in parser?
3/14/17

6
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Bit-shifting Sorrow

I am getting a segfault due to improper bit-shifting in my assignment of VPN2. What is wrong with this? I drew out the w
3/14/17

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PageTable_set_entry index

The header file said that "A NULL pointer means that the 'index'-th page in 'pt' has not been assign
3/14/17

2
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64 or 32?

Can anyone explain this? Doc told us we need 64 bits to get VPN1,VPN2, VPN3 and offset. However, isn't 0xdeadbeef 32
3/14/17

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Instr [SVN UP] for Parallel Make

Hello, We have added a "set.h" in the includes folder, which you may find helpful (but is not necessary). We a
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3/14/17

2
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num of thread specify by -j

is that the number of working thread? or is that the total number of thread, including main thread?
3/14/17

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memory for the physcial address

I'm looking at the layout of the address for the lab |-------------|------------|------------|------------|--------
3/14/17

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Page_fault and tlb misses

If something does not even have a page table, it seems obvious that it's going to miss in the TLB too. (Or is there
- 1 Unresolved Followup
3/14/17

0
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Parmake Dictionary

The documentation doesn't mention the dictionary, but we have header file for it. Can we use it for the MP (ie, is i
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3/14/17

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key for TLB

key for TLB include MISC part or not
3/14/17

9
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Instr Autograder MP Parallel Make Part 1 Released!

We have released Parallel Make Part 1 AG! Note: Please start working on the MP before the Spring Break. There is only
- An instructor thinks this is a good note
3/14/17

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no pagetable vs no pagetable entry

if we pass in a vpn and a pointer to pagetable_get_entry, and it returns null, how do we know if this is due to its entr
3/14/17

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Instr Cancelling Wednesday Office Hours & Parmake Reminders

Hello everyone. Due to a midterm, I'll be rescheduling my 12pm-2pm Wednesday office hours to 11am-1pm on Friday, and
3/14/17

2
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What does it mean by "The name of the rule is not the name of a file on disk"?

How do we figure that out?
- 1 Unresolved Followup
3/14/17

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Page directory return NULL?

I have question which may seem obvious but I want someone to explain. What if PageTable_get_entry(ptr2, VPN2 ) == NULL ?
3/14/17

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So when's the next midterm?

I'm trying to gauge the amount of stress I will have after spring break. When can we expect Midterm 2?
3/14/17

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PageTable_set_entry

From my understanding, we call this function when there is nothing assigned to the PageTable at the index we want. But w
3/14/17

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MP Grading Clarification

Hey so just to clarify, there are 9 MPs total in the course. Im trying to understand how much they are worth. So Malloc
- 1 Unresolved Followup
3/13/17

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virtual_address bit shifting

I am trying to manipulate virtual_address to extract VPNs and I thought that the virtual_address was supposed to be 64 b
3/13/17

3
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Might be too late but

** Thread 0: barrier wait at cracker2.c:163** Thread 1: (none) at (none):0** Thread 2: barrier wait at cracker2.c:93** T
3/13/17

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PASSED AG no_busy_wait_v1 at 2pm but FAILED it at 6pm?

Passed all v1 tests at 10pm yesterday and 2pm today but failed test_no_busy_wait_version_1 at 6pm today. I'm sure th
3/13/17

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curr_pid in struct vs pid parameter?

I read @1749 but I'm still confused: There is a curr_pid in struct MMU, and a pid parameter in MMU_get_physical
3/13/17

7
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Autograder Timeout

I finished part 2 and got it running earlier, but the autograder says I timed out on all of the big 5 point tests. I don
3/13/17

3
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Mutex around v2_print_thread_result()

Should I wrap a mutex around v2_print_thread_result() to stop Thread 3: Stop after 154713313 iterations Thread 4: Stop a
3/13/17

2
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not creating enough threads

Only 3 out of the 4 threads i've created are getting to my start routine for some reason. I know my pthread_create f
3/13/17

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dictionary's behavior is not same as specification

If I try to get a non-existent key, dictionary_get will abort the program by assertion instead of returning NULL.
3/13/17

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crypt_r() Thread Safety

Hi. So everything is working perfectly fine when I lock around this: try_hash = crypt_r(temp, "xx", &cdata);
3/13/17

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NUM_THREAD + 1

General question in this class... In this problem: https://github.com/angrave/SystemProgramming/wiki/Sample-program-usi
3/13/17

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AG 6 pm???

anyone see their results for the AG at 6 pm yet?
3/13/17

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question about getSubrange

Are we required to use getSubrange for part 2 of the mp? (i.e. will we lose points if the exact ranges our threads searc
3/13/17

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Finding the PageTable Pointer

So I understand that the virtual memory gives us the indices for where to look at for each table. However, I'm confu
3/13/17

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Weird Seg Fault

I'm getting a weird seg fault in my lab. According to GDB, this happened at the clean up part of the code. Program r
3/13/17

3
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"Thread status array are not initialized"

So when I try to run cracker1.c with inputs given by the example, it stops after decoding the five lines of passwords wi
3/13/17

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Segfault on copy constructor

resolved
3/13/17

4
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what is time out bond for the test case?

for example, the total CPU TIME < 60 Seconnds?
3/13/17

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Nevermind
3/13/17

6
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memory leak test

I've ran both part 1 and part 2 with valgrind with multiple different inputs and always got the result All heap blo
3/13/17

2
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Segfault at mutex_lock

Thread 2: ==6083== Invalid read of size 4 ==6083== at 0x5283D44: pthread_mutex_lock (pthread_mutex_lock.c:67) ==6083=
3/13/17

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Version 1 is too slow

Resolved.
3/13/17

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Implementing part 1 with threads

Thread 1: Start donna Thread 1: Password for donna is helloaac (3 hashes in 0.00 seconds) Thread 2: Start eric Thread 3
3/13/17

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HELP: Freeing memory

char **strsplit(const char *str, const char *delim, size_t *numtokens) { char *s = strdup(str); size_t tokens_alloc
3/13/17

3
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Freeing strdup memory and not messing tsan

I'm trying to free the lineToPush memory. char* lineToPush; while((read = getline(&line, &le
3/13/17

2
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Wrong header?

If I included the cracker1.h header in my cracker2.c instead of the cracker2.h, will this have any effect on the grading
3/13/17

4
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graph.h: missing arguments

Should graph_vertex_count() take a graph *g?
- An instructor thinks this is a good question
3/13/17

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Posion Pill

So for stopping the threads, I'm pushing a task* pointer that points to null in my queue and in my work function, I
3/13/17

2
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busy wait test

On the 2pm AG yesterday I had passed the "test_busy_wait" test, but on last night's AG I failed the same tes
3/13/17

4
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The input file is not correct?

So when I run cracker2_easy.in, I fail all the tests but when I run cracker2_hard.in, I get them all right. So I looked
3/13/17

2
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Memory leak

I'm getting a memory leak without an error in my code, does anyone know what this is? ==3712== 36 bytes in 1 blocks
3/13/17

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Copy Constructor Leak

My copy constructor is giving 1 lost block in memory, I have just added what I believe is a deep copy now with mallocing
- 1 Unresolved Followup
3/13/17

18
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Instr Additional autograder run for Password Cracker

Hello, For those of you who have been failing test_v2_sanity, this test case has been updated. (@1826) There will
- An instructor thinks this is a good note
3/13/17

4
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test_one_invalid_password_version_1 test failing

I'm currently failing test_one_invalid_password_version_1 on the autograder. I assume "invalid" means "p
3/13/17

2
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Negative total CPUTime

For some reason when there are cases when the password can't be found, I get a negative total CPU time and thus a ne
3/13/17

10
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Ideal Indirection Autograder?

So, when the autograder ran last night, I got the following scores, all with the same error: Yet, I can't see how
3/13/17

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memory leak somewhere

I'm getting a memery leak somewhere and I always have "n" number of mallocs I still have to free. And "n
3/13/17

2
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Get "stock smashing" error only when running cracker2 on cracker2_easy.in

My cracker2 works on all the other given inputs with no issues, but when I run it on cracker2_easy.in, the program immed
3/13/17

2
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error? password cracker

What does that mean? Ty
3/13/17

3
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Random Failures

So I noticed this while testing the given outputs and then confirmed something was weird by doing the create_examples (w
- 1 Unresolved Followup
3/13/17

2
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Execution Failed

I failed all of the cracker1 memory tests and they all said "Execution Failed". What does this mean?
- 1 Unresolved Followup
3/13/17

4
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Invalid Reads/Writes/Etc.

I'm having strange errors with my memory reads and writes and I cannot figure out why. What I'm doing is putting
- 1 Unresolved Followup
3/13/17

1
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Found correct output, wrong return code

I received this message on test_one_valid_password_version_1 and test_crypt_r_count_version_1. Does this mean my formatt
3/13/17

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Are atomic operations more efficient than mutexes?

As the title asks, are they faster and more efficient? Or are mutexes better to use? I suppose the specific situations i
3/13/17

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are we allowed to #include ?

#include <math.h>
3/13/17

12
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Instr make parallel_make

We have released the Parallel_make MP! We apologize for the slight delay in deployment of this MP :( This MP is locat
- An instructor thinks this is a good note
3/13/17

4
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Weird Errors in Version 2 Autograder?

The autograder fails a bunch of my tests for version 2, with messages like: Could not find cpu usage outputCould not
- 1 Unresolved Followup
3/13/17

3
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super slow for part 1
3/13/17

7
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Undetermined behavior in v1

When I run cracker1 on the first input, the output is about evenly split between the correct output, missing two passwor
3/13/17

3
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Segfault on copy constructor

resolved
3/13/17

3
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Failing test_sanity_version_2 but passing literally everything else

How can I go about fixing test_sanity_version_2? I've tried running it with 30+ generated password cracks and no
3/13/17

1
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Weird error with v1_print_thread_result

cracker1.c:105:5: error: ‘saveptr’ may be used uninitialized in this function [-Werror=maybe-uninitialized] v1_prin
3/13/17

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Is it necessary to use condition variables with barriers for version2?

Or will using global flag variables work just fine?
3/13/17

2
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pthread memory leak

I'm having memory leak in cracker2 that I can't understand... Here's the full heap summary. ==2779== HEAP SU
3/13/17

1
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When do we use getCPUtime and getThreadCPUTime?

the end results return correctly without using these
3/13/17

12
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cracker2 sanity

Hello, I kept failing the cracker2 sanity test. It says that when testing with many passwords, the outcomes do
- 2 Unresolved Followups
3/12/17

4
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Still confused with queue usage

I get stuck by using queue correctly. So I know that I need to create a struct to store the work, then are we provided w
3/12/17

6
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Barriers get deadlocked

I use a barrier (initialized every password iteration) and condition variable (to start/stop the threads) for cracker2.
3/12/17

3
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Long CPU time

For part 1 of password_cracker, I believe I have the correct output, but one of my threads takes significantly longer th
- 1 Unresolved Followup
3/12/17

2
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Do we need a queue for part two?

Also, if one thread finishes should it wait until the whole task is done or move on to the next task immediately?
3/12/17

5
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Same virtual address, same physical address?

Hello, I noticed that in tlb.h, the get address function claims that if the virtual address is the same, the
3/12/17

1
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What's definition of timeout for AG

I failed test-13-thread for version 2 because of timeout. For the example hard input, each password takes me couple sec
3/12/17

2
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tsan

My code works for the original executable cracker1 and cracker2, by when I run ./cracker2-tsan < inputs/cracker2_eas
3/12/17

4
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crypt_r() and crypt_data struct

do we have to use the crypt_data struct and/or the crypt_r in our functions? I thought the hashes were already given to
3/12/17

3
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Question about autograder (header files)

The autograder uses our own header files right? I'm curious since I'm trying to use some helper functions.
3/12/17

3
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Resolved

Resolved
3/12/17

2
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test_12_threads Unknown failure :(

I tested both cracker1 and cracker2 with 12 threads on VM and they both went well. So I don't know how to deal with
3/12/17

2
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Is it possible to do Part 2 without a barrier?

I am not really good at the whole barrier thing (kind of hard for me to conceptualize). Can you get away with just using
3/12/17

9
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Threads

How do you get a return value given a pthread_t? What are the ways a thread can set that return value? What happens if y
3/12/17

3
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how to fill queue

Is it required that we push lines into the queue in separate threads, or can we do that before we create the threads?
3/12/17

4
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Race condition warning

Why did tsan report a warning on my barrier……? The function which the threads are passed in called barrier_wait, and the
3/12/17

2
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Race condition when printing out thread status

I got version 2 of password cracker to work but I noticed that on occasion the text doesn't print out correctly as i
3/12/17

1
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Busy Wait

Does the test_no_busy_wait check cracker2 as well? Because for cracker1 the only "wait" I do is when I pull from
3/12/17

5
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Does the gradebook take into account the 1 lab drop?

I checked gradebook and there's points detracted from lab attendance even though I've only missed one lab. Does
3/12/17

13
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Memory leak from pthread_create

Hi, valgrind reports a memory leak from each thread due to pthread_create (and nowhere else). This occurs even though I
3/12/17

0
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Example from wikibook

Im little bit confused about example. So I know sum+=local is only critical section and to avoid race condition, we
3/12/17

2
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Grade Report

How do we know which test cases are for part 1 or for part 2? I'm trying to make sure I got part 1 completely right
- An instructor thinks this is a good question
3/12/17

3
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When will the autograder run?

Been checking for sometime and haven't seen the autograder for today at 14:00, is anyone else having this issue?
3/12/17

2
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mutex example

pthread_cond_t cv; pthread_mutex_t m; int count; // Initialize pthread_cond_init(&cv, NULL); pthread_mutex_init(&am
3/12/17

4
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Can't compile with crypt_data

I tried compiling the sample code that uses crypt_data and crypt_r from the MP website: and this is the error I got:
3/12/17

2
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Cracker 2 main thread wait

Hi, I'm working on part 2 and I'm unsure how to have the main thread wait for the worker threads to finish crack
3/12/17

5
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Cracker Question: test_use_same_threads

Can you give us a hint about what it actually tests for? I am confused about "Test that same threads were used for s
3/12/17

2
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Grade Cutoffs

I noticed a while ago that according to the course site, in this class, a 91.9% does not guarantee a grade in the A rang
3/12/17

7
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pthread_exit()

pthread_exit(void *) only stops the calling thread i.e. the thread never returns after callingpthread_exit. The pthread
3/12/17

0
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Quiz

Up to which week #, title is the quiz based on? http://cs241.cs.illinois.edu/schedule.html#currentWeek
3/12/17

1
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Burning Question About getSubrange() Function

Hello. I am starting Version 2 and I am very confused about this function: void getSubrange(int unknown_letter_count, si
3/12/17

0
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how to set queue's max_size and other two arguments

Hello! Could anyone give me some hints of setting the queue's max_size? I didn't do the relevant lab well so I a
- 1 Unresolved Followup
3/12/17

3
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Busy wait

Hello, Good morning. I am failing the test_busy_wait on the auto grader last night. I am pretty sure that I did
3/12/17

6
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Lost I card

I have a quiz tonight but i lost my i card. What can i do?
3/12/17

4
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Reason for timeout

Is there any other reasons than deadlock that will make my code time out in password_cracker AG? I tried multiple inputs
3/12/17

4
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number of hashes

Out of curiosity, does the crypt_r count test check the number of hashes we actually do or the number we give to our pri
3/12/17

8
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busy wait

I failed the test saying I have unnecessary busy wait. How can I try to find this in my own code/with the tests provided
3/12/17

2
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Quiz Lectures

Which lectures does the quiz exactly cover?
3/12/17

4
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Number of iteration is not right

I got the error saying that my number of iterations for v2 is not correct. I am wondering what could cause this problem.
3/12/17

5
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thread_id extremely large

I use an array to hold thread id. But it turns out that thread id is extremely large num like 140737341228800. Any ideas
3/12/17

2
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getThreadCPUTime() Usage

My first instinct was to call this function twice, and then take the difference between the two times in order to get th

▾ Week 3/11 - 3/18

3/13/17

4
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Testing password command line

is this the right way to test cracker1? ./cracker1 < inputs/cracker1.in thanks
3/13/17

4
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How to use queue_push

Hello! When I tried to use queue_push, what "element' looks like? Why the following code won't work? char el

▾ Week 3/5 - 3/11

3/11/17

0
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All threads receive same data

For part two, I create a queue that I pass into pthread_create. For each thread, I pass in a small queue which only has
- 1 Unresolved Followup
3/11/17

2
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Using Queue

Do we have to use the queue for password cracker?
3/11/17

11
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Getline not working back-to-back?

I'm breaking my head over this. I am trying to make an array of tasks. I use getline once to get number of tasks to
3/11/17

2
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Where to find question to review?

I have completed quiz3 and I want to review it. I wonder where can I find those question?
3/11/17

3
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tsan never finishes

When I run cracker 1 with tsan, no output is printed and the program runs indefinitely, when without it my program speed
3/11/17

4
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Quiz 3 Dining Philoshopher

Does the quiz 3 cover up to dining philosopher?
3/11/17

2
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Cracking Confusion

So if where given an input like "hello...", I'm confused as to how we go about cracking the password. Do we
3/11/17

0
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Is it possible for two threads to simultaneously lock a global mutex?

Both will see that the mutex is not locked therefore proceed to lock it. EDIT: And how is this a valid algorithm: write
3/11/17

13
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Strange behavior

For password cracker pt2, Im grabbing a newline, putting information into a task struct for each thread, then the thread
3/11/17

0
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Real Page Table Functionality?

So, in this lab, the third level of the page table holds the full 64 bits of the physical address...which confuses me.
3/11/17

8
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How to crack password

Hi, I'm confused on how exactly to go about cracking passwords inside the worker threads. I've looked through th
3/11/17

7
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Synchronization strategy for cracker1

Hello! I am a bit confused with my naive synchronization strategy for cracker1, which may miss so many requirements that
3/11/17

3
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Instr Autograder Lab Ideal Indirection Released!

We have released Ideal Indirection AG! Schedule: "2017-03-12 22:00", "2017-03-13 22:00", "2017-03-
- An instructor thinks this is a good note
3/11/17

17
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Instr Autograder MP Password Cracker Released!

We have released Password Cracker AG! Schedule: "2017-03-11 22:00", "2017-03-12 14:00", "2017-03-1
- An instructor thinks this is a good note
3/11/17

1
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Output order

Does the order of the output matter? Should the thread which finds the correct password always print first? Also, shoul
3/11/17

0
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Thread_id mysteriously increased

I pass thread_id to each thread by (void *) & id However, even if I did not do anything to "id" in each thr
3/10/17

0
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Page Table Size

I'm a bit confused by the size of the PageTable struct's entries array. If we are supposed to extract vpns that
3/10/17

2
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what is a disk read

I'm not sure what is meant by the disk and information that is stored on it?
3/10/17

2
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strplit

Are we allowed to use the strplit() function/code that we have used in previous assignments?
3/10/17

0
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Test case sols

Is there a way to check the solutions to the given test cases?
3/10/17

5
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How to set queue elements to null?

I am aware that in the end of the main method in Part 1, we have to tell all the threads to stop and then call pthread_j
3/10/17

1
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sscanf VS strsep

I just wanted to give everyone a heads up: Originally, to do the splitting in password cracker, I was using strsep with
3/10/17

0
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Passwork Cracker TSAN on Autograder?

So, I was wondering if there will be checks for TSAN error on the autograder? Currently, I am getting a warning of a ra
3/10/17

0
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How to register half-semester CS241 course?

Hello! I just heard from my advisor that if feeling struggling in this course, there is an option of taking a half-semes
3/10/17

0
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Flush TLB for different processes?

I'm working on the lab and was wondering what do we do when we get a new pid since the TLB doesn't seem to save
3/10/17

0
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Password Cracker AG

Is it going to run tonight?
3/10/17

12
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Segfaulting at Queue Pull???

Hello, I just finished writing all my code for Part 1 and I am getting a major segfault preventing me from testing. I ra
3/10/17

5
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Thread ordering?

For part 2 of the password cracker, does thread 1 always have to do the first part (aaa.. to some letters) and then the
3/10/17

4
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Instr Planned VM Outage

Dear CS241 Students: The CS241 VM's will be unavailable due to maintenance on Monday March 20th, 2017 beginning at
- An instructor thinks this is a good note
3/10/17

2
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What to put on feedback form

What should I put for the assignment under the feedback form? There's no deadlocked_diners option. Thanks!
3/10/17

2
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VM Connection Problem

My VM is still cannot work. I'm not sure if there is still other problems, or if the Engineering IT is still working
3/10/17

2
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elapsedTime

When should we start clocking elapsed time we used for v2_print_summary, i.e., what time interval is it supposed to repr
3/10/17

2
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Can you append a char* to a char** without knowing the index you're appending to?

I have a list of passwords that I'd like to update using a recursive function, therefore I don't have the index
3/10/17

4
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strsplit/sscanf

How can you assign variables like username, hash, and password to parts of the line using sscanf? I was planning on usin
3/10/17

17
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Can't connect to vm

I can't connect to my vm. Is anyone else having this problem? I am trying to access it from DCL computers.
3/10/17

3
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How to fix VM problem?

I posted this question here @1730 The problem was my VM, not my code. My code worked fine when running on my frien
3/10/17

3
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String formatting different among input files

May we have consistent string formatting from the input files? For part 2, cracker2_easy.in has slightly different forma
3/10/17

4
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waiting on empty queue vs file finished

Hi, so I was wondering how to deal with this possible problem (or am I interpreting the docs incorrectly?): Let's s
3/10/17

1
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CSP Peterson's algorithm

The wikibook has this as the algorithm: raise my flag turn = your_id wait until your flag is lowered and turn is yourid
3/9/17

0
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Password Cracker Autograder?

When will the autograder runs begin for this MP?
3/9/17

5
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how the start function read file

pretty confused with how to let start function see argv[]. because the start function only have one parameter thread_cou
3/9/17

3
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Part 1 slow total time

The runtime for each individual thread looks okay, but the total time is really slow. My threads run concurrently and
3/9/17

0
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Running 'make' doesn't change the tsan executable - you have to run 'make tsan' everytime

Maybe i am stupid therefore got stuck here for hours, but letting everyone know so others won't have to go through t
- An instructor thinks this is a good note
3/9/17

0
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Why do we need the barrier for MP part 2?

Right now, I'm creating the threads and joining them inside a while loop that checks if getline() has next. Since p
3/9/17

0
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Successful/Unsuccessful Passwords

Hi, In the docs it says that the main program will take care printing the number of successes: "After all the worker
3/9/17

2
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man pages for mutexes?

Apparently the "built-in" man pages don't have entries for mutexes/barriers. To get them on the VM, I had to
3/9/17

1
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Can the ThreadSanitizer link on the mp page be updated?

And, why am i getting a race condition even when i do: pthread_mutex_lock(&m); size--; pthread
3/9/17

0
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Accessing Virtual Address

Hello, I'm sorta confused about the "virtual_address" parameter. Is the address given when dereferencing wi
3/9/17

0
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Initializing threads

For the MP, when we initialize the threads, I'm confused about whether we use the function in thread_status to initi
3/9/17

0
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Queue pulls only give last element

I made a file of 15 examples to pass to the first password cracker. I then put them on the queue using the push function
- 1 Unresolved Followup
3/9/17

1
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version1 thread id

In version 1, when we print the thread_id, should we use gettid to get it or just use an integer id which main thread as
3/9/17

0
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Interpreting Output of Test Program

I'm seeing "Process [42] tried to access [0xdeadbeef] and the MMU got an invalid entry" a lot in the output
3/9/17

0
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spring break mp

Just making sure, we get our next mp released on the following monday, but we will have the allotted 2 weeks without inc
- An instructor thinks this is a good question
3/9/17

1
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Instr Malloc Feedback

Here is the feedback we received from Malloc assignment. Thank you to all those who submitted feedback. Interestingly..
- An instructor thinks this is a good note
3/9/17

3
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George's password not found

In my code, Crypt_r(xzzzzy) gives a different output than the input file. Thus my output says that George's password
3/8/17

1
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Instr Ideal Indirection Released!

(Sorry, couldn't come up with a pun with this one...) The lab Ideal Indirection is released ! Please svn up in orde
- An instructor thinks this is a good note
3/8/17

0
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So the password is assumed to be made up with lowercase letter, right?
3/8/17

0
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Seg fault using incrementString function in utils

I saw this function in utils, after reading the code I thought it was used to increment candidate string when doing sear
3/8/17

0
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should set_job_duration come after hire_intern?

or is it the other way around?
3/8/17

0
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Can't use gdb?

Im trying to use gdb to test my password cracker, but when I try to pass in a file as an argument: gdb ./cracker1-debug
3/8/17

0
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MP redo

I heard that we are allowed to redo 1 2-week MP or 2 1-week MP's. Is that still the case? And if so, can we get an a
3/8/17

0
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Input file

The file will not change while threads are working, right?
3/8/17

0
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Autograder

How long is the run for the deadlock diner AG? waiting on the 2 pm run.
3/8/17

1
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Is there any way we can get number of companies?

I'm trying to solve by using arbitrator. I found num_companies is defined on simulator.c as global variable(static i
3/8/17

2
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strsplit

We've gotten this function in the past, is there a version provided to us this MP? I didn't see it looking throu
3/8/17

0
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deadlocked_diners: what does "the ith company likes to work with intern i%k and i%k" mean?

Hello! I am confused with the sentence " the ith company likes to work with intern i%k and (i+1)%k". Does it
3/8/17

0
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password cracker part 1 confusion

Hello, I noticed that in the website, the spec for password cracker version 1 says "Use multiple threads t
3/8/17

5
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Weird stdin reading behavior?

So, currently, I have a loop that, in the main function, uses a getline() to read from std in and then place that input
3/8/17

0
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Office hours

Were office hours cancelled from 9 to 11? I thought I saw people on the calendar earlier...
3/8/17

0
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"Solution not fair" on AG but not on VM

When I run these tests on my VM, with my code, they run in a "fair" way, closely matching the reference. Yet on
3/8/17

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Lecture Song Requests

Brand X - Nuclear Burn Cactus - Evil Chris Squire - Lucky Seven Genesis - Duke's Travels Genesis - Lamb Lies Down on
3/8/17

0
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One intern testcase

Here is my output for one intern. ./good_company 3 1 100 it's exactly the same as the reference, but why am I fail
3/8/17

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Dijkstra solution

when I try to use the dijkstra's solution ( making the company to pick up the lower number intern), it seems like th
3/7/17

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Password input

I just want to make sure that we are reading lines from standard input(stdin). Or do we need to indicate which file we a
3/7/17

0
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Checking if a thread was locked

Can we put pthread_mutex_lock(...) into an if statement to check if we actually get the lock? If not, how do we check if
3/7/17

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Is there solution to the google form?

in the title
3/7/17

0
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Make error

Hi all, When I do make I get this error: /usr/bin/ld: final link failed: Bad value collect2: error: ld returned 1 exit s
3/7/17

1
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V2 Password Recovery output

For V2 of password_cracker, even though I call all the requisite format.h functions (v2_print_start_user, v2_print_threa
3/7/17

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Fairness

Fair (all companies should get a roughly equal number of billable days) You must be within 90% of than the reference sol
3/7/17

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performance

Performant Performance will be judged against the reference solution (good_company_reference) and measured by total bill
3/7/17

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task queue

do we have to write our own task structs that our queue will hold? i have not really found any provided task struct in q
3/7/17

4
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Reference vs Implementation

I noticed that on most cases (like the one specified in the docs) my implementation is close to the reference. However,
3/7/17

2
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Input File - Password Cracker

Am I missing something or is there no input file name passed to the start() function? How do we know which file to read
3/7/17

0
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Walking Away From Malloc Like...

It's been a long ride, fam
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3/6/17

2
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size after coalescing and split

if I coalescing two free memory block with their meta_data say like, m1,m2. is the m1's size become m1->size+
3/6/17

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Can we use system call in Password_cracker?

Can we use gettid in Password_cracker?which is only for linux system?
3/6/17

2
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Writing to data

I am implementing fragmentation using boundary tags, but it says that I am segfaulting when I try to create a new bounda
3/6/17

2
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Strange Test 5 results

I'm getting some strange behavior when running Test 5, a couple of the bytes stored in my dictionary are being blank
3/6/17

1
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Instr [SVN UP] Password Cracker queue.h and cracker2_easy.in

There were some non thread safe functions included in the "queue.h" file. Please take a look at @1673. Thes
- An instructor thinks this is a good note
3/6/17

3
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Issues with cracker2_easy.in

It looks like cracker2_easy.in has the full output of the example tool in it. Is it supposed to be like that?
3/6/17

0
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reading from stdin

Do we assume that the number of threads is the number of lines to read from stdin, or do we continue to read from stdin
- An instructor thinks this is a good question
3/6/17

0
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Failed to call queue_empty

The compiler shows that "undefined reference to `queue_empty'". Do you provide the queue_empty function
- An instructor thinks this is a good question
3/6/17

0
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Password Cracker Autograder Criteria

How will the autograder determine success or failure for the test cases it runs on our solutions? It says "times and
- An instructor thinks this is a good question
3/6/17

6
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Splitting Problem

Tried implementing a splitting implementation in my malloc, but I'm getting a strange error. Was testing in test
3/6/17

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how do we know who the TA in charge is for each lab session?

i cannot find it on the website
3/6/17

0
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contest page not running on latest commit?

so i svn committed earlier and i checked that I passed all the test cases on the contest page and now it went back to no
3/6/17

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missing lab session

I have a very important appointment on Thursday during my lab session. I know there is one drop for attendance, but is
3/6/17

0
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How many tests can we pass without splitting/Coalescing?

^
3/6/17

1
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How does the machine deal with booleans?

I changed a variable I had in my meta_data struct from an integer to a boolean. I understand that the way my struct is c
3/6/17

0
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Instr Wednesday OH 10-12 Cancellation

Hi all, I'm Steve. I have to move my Wednesday's office hour (10AM-12PM) this week to next Friday (Mar-17) 10-1
3/6/17

2
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Where are all the TA's?

There were supposed to be 2 TA's from 3-4, yet nobody is on the queue. Will they be coming later? The queue is growi
3/6/17

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chara queue

I am almost next on the queue, the bid for my spot starts at $49.95.
3/6/17

3
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Memory failed to allocate

$ ./mcontest testers_exe/tester-4Memory failed to allocate![mcontest]: STATUS: FAILED=(1)[mcontest]: MAX: 214912[mcontes
3/6/17

4
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"both interns need to be locked by the same company before hiring"

I get this message when I try to run good company. I'm not sure why: I either lock, hire interns using company, and
3/6/17

6
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Break malloc hardcode?

Will instructors be attempting to break the "cheese" code of people who have hardcoded the test cases, for the f
3/6/17

1
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testers

Can you guys remove test 9 cuz I can't pass it thanks
3/6/17

7
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Test passed before but fails now

My test 4,5,6 and used to pass on my machine AND the autograder (got a 7/7) but now when I run them they fail on my mach
3/6/17

0
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Queue.h mem leak?

I started implementing my cracker1.c when I noticed that queue.h never seemed to call my destructor for the data in queu
- An instructor thinks this is a good question
3/6/17

2
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how do I split my blocks

Given a freed block and then a malloc with request with left over space how do I move to the point of my new block when
3/6/17

6
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passing test 11-advice?

I'm still unable to pass test 11 because of the memory limit. however, i do implement splitting and coalescing. does
3/6/17

1
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Instr Password Cracker 23690fd759f17135ec9879b56ff2600c!

We have released the Password Cracker MP! This mp is located in your svn repo at: https://subversion.ews.illinois.edu/sv
- An instructor thinks this is a good note
3/5/17

14
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not passing 5 companies 1 intern but reference doesnt either?

I get error You did not bill all 5 companies but the reference doesn't either Thanks EDIT: formatting
3/5/17

2
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how to find grade

how do I know which one of the submission in the contest page is mine?
3/5/17

5
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Instr Autograder Lab Deadlocked Diners Unlocked!

We have released Deadlocked Diners AG! Schedule: "2017-03-05 22:00", "2017-03-06 22:00", "2017-03-
- An instructor thinks this is a good note
3/5/17

2
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Strange Test 5 Segfault

I am segfaulting in Test 5 and I ran it through GDB. However, I'm not sure what to make of this: Thread 2.1 "tes
3/5/17

3
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call company_hire_interns more than once

After I lock both interns, is it okay to call company_hire_interns(company) multiple times before I unlock them? When I
3/5/17

4
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Segfault when accessing elements in my struct

When I split a block I do something like this, where size is the new smaller size meta_data * split = (meta_data *)(((
3/5/17

16
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memcpy

Has anyone else been struggling with memcpy segfaults because of overlapping memory/have advice on how to fix it? update
3/5/17

6
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mcontest failed=(66)

I svn up'ed just recently, and am now getting "Unable to find a required memory allocation function. [mcontest]
3/5/17

3
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My addresses are being concatenated together

The GDB looks like this: (gdb) print tail$7 = (meta_data *) 0x129ec98c(gdb) print tail->prev$8 = (struct _meta_data
- 1 Unresolved Followup
3/5/17

2
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Realloc'ing a smaller size

When we realloc a smaller size, should we split or just return the same pointer? If I split, I only fail test case 4, bu
3/5/17

4
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Subversion down?

Is Subversion down for anyone else? Anytime I try and connect it says I can't connect to it. I can't commit eith
3/5/17

2
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Quiz 3 content

What will quiz 3 cover?
3/5/17

3
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Different result when running tester-8 and tester-11 on gdb and mcontest

When I ran my using ./mcontest testers_exe/tester-8 and ./mcontest testers_exe/tester-11 I got the data allocated outsi
3/5/17

2
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does the autograder change?

I remember my code passing for a specific test yesterday, but it doesn't pass today when i test it locally. I didnt

▾ Week 2/26 - 3/4

3/4/17

4
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Dijkstra's Solution Problem

I implemented Dijkstra's Solution but I'm running into the problem mentioned on the wiki book where it prioritiz
3/4/17

10
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Data allocated outside the heap

I am getting the following error on a lot of the tests but for most of them I am using less than 2.5gb. For example on t
3/4/17

2
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Failing test locally but passing on Contest

If I'm failing a test locally, but passing on the contest page am i fine?
- An instructor thinks this is a good question
3/4/17

2
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Please help me add to head

I originally had only a singly-linked list as my data structure for malloc. Now I am trying to transform my singly-linke
3/4/17

7
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Test 6 - Outside Heap

I'm passing everything except test 6, where it says data allocated outside of the heap. I have splitting/coalescing
3/4/17

7
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deadlock_diners

When will auto grade start to run ? thanks
3/4/17

0
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Data allocated outside heap error.

Anyone else getting this error. I check if sbrk returns -1, but i am still getting this error. What might this be?
3/3/17

6
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Lecture Video is green?

Are there any fixes to the lecture video screen turning green when the laptop screen is shown for Professor Angraves lec
3/3/17

5
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Are we allowed to call Company_have_board_meeting(company);

bad_company doesn't call it but the comments above the function says "Call this function so that your company ca
3/3/17

0
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Strange GDB Behavior

I am trying to debug a random segfault in my test 5. I have used the set fork-follow-mode child thing before, but now it
3/3/17

6
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contest page acting weird

It looks like this and doesn't allow you to scroll
3/3/17

0
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Malloc Part 2 Grade

On which tests will our code be graded? The AG for the contest or the test provided on the MP? For example, if my code f
3/3/17

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failed=(1) for test 12

Really not sure about this error...all my other tests pass except 12, which outputs STATUS: FAILED=(1). The seems to ind
3/3/17

4
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modifing test file

Is it possible to modify files like test-tils.h to help me debug? It's set read-only. Thanks.
3/3/17

3
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Casting and then accessing elements of struct

I am trying to implement splitting up free blocks if the requested malloc size if smaller than a free block available si
3/3/17

7
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How hacky can our malloc be?

So, people are apparently figuring out how to play the malloc game very well, for instance, using no metadata for test o
3/2/17

4
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Test case 11 uses less than 2.5 GB

My test case 11 uses less than 2.5 GB for both max and average and it is passing locally but it is also failing on the c
- 2 Unresolved Followups
3/2/17

3
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Instr good_company-reference redeployed - svn up!!!!

Good_company-reference executable has been redeployed for Deadlocked Diners lab. We apologize for the confusion. please
- An instructor thinks this is a good note
3/2/17

2
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sudo Reboot

I sudo rebooted my virtual machine and now I cannot connect to it. I have waited more than 5 minutes. Is this normal?
3/2/17

4
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failing test 8 on contest but not locally

Test 8 running Memory was allocated and freed! [mcontest]: STATUS: OK [mcontest]: MAX: 1789569771 [mcontest]: AVG: 16659
3/2/17

5
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./mreplace gives zero heap usage

My ./mreplace is giving the following results: $~/temp/malloc$ ./mreplace testers_exe/tester-4 Memory was allocated, use
3/2/17

2
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Understanding partial ordering

If we arrange all threads except for the last to lock the left intern first, and the last thread to lock the right inter
3/2/17

5
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Don't we need to know the number of interns in order to use Dijkstra's solution?

Interns are just represented as mutex's, so how can we check for the "lesser" intern in order to use Dijkstr
3/2/17

0
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Interpreting Output for Deadlock Lab

I'm not quite sure what's going on with the billed hours between the reference implementation and my implementat
- An instructor thinks this is a good question
3/2/17

14
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Instr Contest AG Restart

We are restarting contest AG with slightly different allocation parameters. It'll take some time to reflect everyone
- An instructor thinks this is a good note
3/2/17

0
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passing contest in VM but not contest

I have tested with ./run_all_mcontest.sh and passes all tests, but on contest, I failed test 10. How could this happen?
3/2/17

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Is the online contest page broken?

My coalescing function is broken so I'm not using it at the moment, but, I'm passing every test case according t
3/2/17

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Potentially-Useful Debugging Macros

As everyone's likely noticed, printf cannot be used in much of the malloc MP. There are various ways of getting arou
3/2/17

14
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Instr Autograder MP Malloc Part2 Allocated!

We have released the Malloc Part2 AG! Please note this ag will take extremely long time. It takes about 5 - 10 hours.
- An instructor thinks this is a good note
3/2/17

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Is lab Google Form graded or not?

The Deadlocked Diners documentation says that the Google Form isn't graded, but there's a message at the end of
3/2/17

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Arbitrator or Arbiter

I know this is not an English class but shouldn't the word "arbitrator" in the Lab slide be "arbiter"
3/2/17

2
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How to check Lab Attendence

Question: is there a way to check Lab Attendence? I believe i wasn't marked present for a lab when i looked in Chara
- 1 Unresolved Followup
3/2/17

0
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Where to find practice midterm score?

I didn't really understand how to see my grade (score) on the practice midterm. Will this be posted anywhere? I'
3/2/17

0
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Lecture Song Request

Blank Space by Lawrence Angrave and Taylor Swift https://www.youtube.com/watch?v=awFuyfL-IeY
- An instructor thinks this is a good note
3/2/17

4
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Instr pthread_mutex_unlock( &deadlocked_diners )

Deadlock Diners lab has been released! Please svn up in order to see the assignment. Have fun :) !! The docs are here
- An instructor thinks this is a good note
3/2/17

1
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Memset segfault?

I got seg fault in test 12 and then I ran gdb with it and caught the error at memset(ret, 0, num*size) in realloc. I wo
- 1 Unresolved Followup
3/2/17

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Malloc Testing - Issues

I am confused here, on my last commit which was monday night. I passed all test cases except for number 10.....now when
3/1/17

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does freeing have to happen after the mutex unlock?

I am not sure whether the freeing of the memory has to happen after the unlock or before the unlock. or does it even ma
3/1/17

3
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How would someone check for deadlock and race conditions?

For race conditions, do you just create a multi threaded program and run something and if output is different everytime
3/1/17

0
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queue not fifo error

When I look at my autograder I see that I fail to pass some of the queue tests because my queue isn't fifo. Can anyb
3/1/17

2
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Using Less Memory on Test 9

Any ideas on how to use less memory on test 9? I've tried implementing everything in the wikibook, but I'm still
3/1/17

1
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pthread_cond_signal

To make sure the barrier is reusable, do we loop through the number of times the barrier has been used via times_used an
3/1/17

2
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barrier_wait

I've been trying to implement a reusable barrier for a while and I think I'm close. If I'm doing a normal on
3/1/17

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Instr Malloc Contest updated

Hello everyone, The contest has been updated with a strict memory limit of 2.5GB. If you exceed this memory limit, you
- An instructor thinks this is a good note
3/1/17

16
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Queue Memory and Queue Stress Test

So I failed Queue Memory and Queue Stress Test. I found out why I failed Queue Memory now (I freed everything but the qu
3/1/17

13
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Queue Unbounded

Hey I keep on failing test: Queue Unbounded - in the detail it said it timed out. Can anyone shed some light as to what
3/1/17

2
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Who should I be emailing to go to the 7:30 discussion ADH instead of my normal one?

Enterprise doesn't seem to have an email for the leads.
3/1/17

3
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Semamore negative value

What if a semamore value is negative? (invalid input) do we need have a check for that or can we just assume that the us
3/1/17

19
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Random Failures with Malloc AG?

I have been passing test 8 on malloc for quite some time now, but randomly on the autograder page, it shows that I am no
- 1 Unresolved Followup
3/1/17

3
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Has the 2PM autograder run yet?

Still not seeing my grade
3/1/17

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TIME: 0.000000 doesn't seem right

./run_all_tests is giving me the following for test 9 and 10 ...Test 9 runningMemory was allocated and freed![mcontest]:
3/1/17

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When testing semamore

I've tested semamore through main() 1) initialize 100 threads 2) initialize semamore 3) init mutex 4) with loop, eac
- 1 Unresolved Followup
3/1/17

2
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Fail to semamore use only

I passed every test except semamore use The AG says time out. Any suggestion? Thanks in advance
3/1/17

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Queue Pulling When It's empty

resolved
3/1/17

3
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pthread_cond_signal in queue

Suppose I have a thread-safe queue with a small positive max size, and that with operating system's scheduling, ther
- 1 Unresolved Followup
3/1/17

2
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Do test constants change for the contest?

I pass test 10 locally but not on the contest. To pass it locally, I rely on constants defined in the test files, like
3/1/17

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Instr Moving Office Hours to 5-8pm

Hey guys, Sorry for the last minute update, but I'll be moving my OH today from 12-2pm to 5-8pm. Hopefully this won
3/1/17

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Song Request Before Lecture

Sultans of Swing by Dire Straits Sultans of Swing (with lyrics): http://youtu.be/2jH74e3Qo9k
3/1/17

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Question about contest page

I have saw the post that Malloc contest page is now online. However, when I go into the contest page I still saw a lot o
3/1/17

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Performance Points w/ Contest Page

It looks like the contest this year has performance points calculated differently than the performance points section of
- An instructor thinks this is a good question
3/1/17

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Instr Malloc Contest is Live!

Dear system programmers, It's the moment you've been waiting for! Check out the New and Improved Malloc contes
- An instructor thinks this is a good note
3/1/17

2
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some questions

I don't really understand about some things: 1. when you're making shallow constructor/destructor (aka passing
3/1/17

5
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Not Seeing 10 PM Autograder Results?

Is the autograder still running? I have cleared my browser cache multiple times and I still can't see my 10 PM 2/28
3/1/17

4
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not really sure what pthread_cond_wait does

On the man page it says functions shall block on a condition variable. They shall be called with mutex locked by the ca
2/28/17

1
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glibc... T_T

glibc failed tester 11.... so sad
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2/28/17

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How often/what time does the malloc leaderboard update?

Just want to know when I should have my commits in. Is it the usual 10 pm (following the autograder pattern). Thanks!
2/28/17

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rendezvous_sol.c test

I'm using the rendezvous_sol code to test my semamore.c functions. when running the rendezvous_sol.c file, most of t
2/28/17

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How does a semaphore acts as a mutex

sem_t s; sem_init(&s, 0, 1); sem_wait(&s); // Critical Section sem_post(&s); So the semaphore's count
2/28/17

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Keeping memory alignment?

So, until now, I had not worried about memory alignment for malloc, and it hadn't caused any issues. Now, however, w
2/28/17

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barrier_destroy

Are we assuming the user is responsible for freeing the barrier struct itself when calling barrier_destroy as in semamor
2/28/17

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test error

queue_tests.c:24:14: error: incomplete definition of type 'struct queue'int c=(int)(q->size); ~^./
2/28/17

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Instr Update to queue.h

We've updated queue.h to remove the comments about "thread-safety".You do not need to worry about what you q
- An instructor thinks this is a good note
2/28/17

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Contest percentages

Can someone please fix the contest percentages? The rank 1 person has the lowest performance...
2/28/17

2
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Note: If thread-safety is off, queue has no max_size.

What does this mean? If max_size < 0, we assume there is only one thread?
2/28/17

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Serious Questions About Midterm 1

I would appreciate it very much if course staff would answer the following questions about Midterm 1: In terms of mater
2/28/17

2
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Test 4 runs on VM but fails autograder.

On my VM, all tests are passing currently, but the autograder ran last night and failed test 4 with error code 91 (memor
- 1 Unresolved Followup
2/28/17

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Do you guys compile the MPs on your local machine?

How do you do it? I don't want to go to an ews station primarily to work on an MP, what other options do i have? Ple
2/28/17

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thread distinct variable

if I want to add a variable(attribute) that each tread has a distinct one,but do not shared between each thread,also pre
2/27/17

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It's hey in the lead!
2/27/17

2
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Test 5 Segfault

I'm getting a segfault in Test 5, however, its after around 700-800th iterations through the loop. Does anybody know
- 1 Unresolved Followup
2/27/17

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Test 11 for Malloc Memory?

So, test 11 allocates a HUGE amount of memory (2,147,483,648 bytes, to be precise), which I guess should be fine, but I
2/27/17

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how to use unsigned int times_used in barrier

I believe this variable is for number of times we use such barrier, but I don't know how it could help me implement
2/27/17

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Failing mcontest but not mreplace

When testing with malloc's tester-5, my code works for mreplace but fails with mcontest. It gives Data allocated out
2/27/17

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Free clafication

I am sure my free takes a lot of time. Can anyone help me to clarify what should we do in free with explicit free list.
- 1 Unresolved Followup
2/27/17

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Boundary tag checks

How would we check if we are outside the heap with Boundary tags? Meaning if I subtract from my meta_data structure to g
2/27/17

4
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heap memory

Say we have void * ptr = sbrk(0);void * m = sbrk(16); is the 16 bytes of memory immediately after ptr? Ptr is now point
2/27/17

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Data Allocated Outside the Heap

Data allocated outside of heap. Calloc/Malloc/Realloc returns a ptr: 0xffffffffffffffff. I keep getting the following er
2/27/17

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Alignment

Is it better to Align memory to a multiple of 4 rather than 16 to save memory?
2/27/17

3
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Instr Shell Feedback

Thank you all for your feedback! Fun fact: Shell is the second most disliked assignment, behind Extreme Edge CasesYou ca
- An instructor thinks this is a good note
2/27/17

4
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What constitutes a timeout for the autograder?

All of my part 1 tests take under 1 second except for my test 6, which averages at 9.5 seconds. To clarify, all the part
2/27/17

2
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Autograder

Last night the autograder said I passed all the tests, but today it says I'm failing test 2. I've always been fa
2/27/17

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tester 2

When running test 2 I keep getting a time out error. It looks like my free is taking up a lot of time, any advice on how
2/27/17

11
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reusable barrier

I believe I correctly implement a one time use barrier but I'm a little lost on how to tackle making it a reusable b
2/27/17

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queue_pull

"If thread-safety is off, assumes queue is not empty." Does -1 max_size also imply that thread-safety is off?
- An instructor thinks this is a good question
2/27/17

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Dequeue question

My understanding is that void *queue_pull(queue *this) should return the address the the data of the first node. If that
2/27/17

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Does Queue Need to be Constant Time on Both Ends?

Do we need to make our queue push and pull constant time on both ends? Right now I have it as constant time on push but
- 1 Unresolved Followup
2/27/17

1
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Test2

For my test2, the first 202 indexes match the correct data but for some reason index 203 holds a very large disproportio
2/27/17

1
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Instr Tuesday 6-8pm OH rescheduled

Hello! Due to a midterm tomorrow night, I'm rescheduling my tuesday office 6-8 office hours to Wednesday 2-3pm and 7
2/27/17

10
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queue copy constructor segfaults

I'm getting some kind of race condition where calling the queue's copy constructor on the data passed in results
2/27/17

5
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0-sized Queue

In queue.h, we're told not to block if max_size is non-positive, and to block is max_size is non-negative. How shou
- An instructor thinks this is a good question
2/27/17

2
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Malloc Tester-11 Data Allocated Outside of Heap

So this the only test I'm failing and I'm wondering what exactly I can do about this. I fail the test after the
2/27/17

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Trying to look at my old commit

I'm having an issue where, I'm trying to view my old alloc.c by clicking on my old commit, but the page when I c
2/27/17

6
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Segfault

So I'm getting a segfault (signal 11) when I run the first few test cases, but valgrind isn't catching it. Any i
- 1 Unresolved Followup
2/27/17

10
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Queue AG Tests

I implemented my queue and ran a bunch of parallel tests on it, and it seemed to work on all the extreme edge cases. So
- 1 Unresolved Followup
2/27/17

5
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Pass 1-6 (except 4) on my machine but fail all of them for autograder

Just as the header says, for the first round of tests I can run it just fine and show it passes for all of 1-6 (except n
2/27/17

3
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Instr Autograder Unknown Error in Lab Splendid Synchronization

If you received this message for Lab Splendid Synchronization autograder, Testcase: Semamore Use, the actual feedback is
- An instructor thinks this is a good note
2/27/17

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Malloc test6 memcpy

When debugging malloc, I got this message from gdb Thread 2.1 "tester-6" received signal SIGSEGV, Segmentation f
- 1 Unresolved Followup
2/27/17

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Invalid Memory Question

In the code above, I am not sure why I get a segmentation fault when trying to set the blockSize of newNode. When I use
- 1 Unresolved Followup
2/27/17

2
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Could we get a bonus evening AG run today?

Like we had in previous MP's? A 6 PM or 8 PM autograder run would make my day.
2/27/17

6
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Initialization to Size of -1?

Why are the default constructors in the queue for the synchronization lab initialized to -1? Won't this be an issue
2/27/17

5
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Instr Mini Valgrind Feedback

Sorry to get this to you so late! HOW CLEAR WERE THE DOCS? Count5Mean7.4Median7.0Mode7.0 WHY DO YOU FEEL THE DOCS WERE
- An instructor thinks this is a good note
2/26/17

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Passed AG but failed local test

When I was running my code on tester-3. I got a data allocated outside of heap error (STATUS 91). It appeared that my m
2/26/17

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Test 4

I've been writing code to fix test 4, and it works fine on small cases (1024 and 256 are the two values I've bee
2/26/17

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Advantages of doubly-linked list

"Better performance can be achieved by implementing an explicit doubly-linked list of free nodes. In that case, we c
2/26/17

4
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Boundary Tags necessary?

I'm implementing mine with a doubly linked list using header data that includes next and prev pointers. Is there an
2/26/17

2
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Coalescing

I sort of understand how coalescing works, I think. If there are adjacent blocks marked as free you can combine them I t
2/26/17

4
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How to call our own malloc

How can we make sure that our functions are calling the version of malloc that we wrote ourselves, for example I'd l
2/26/17

6
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Instr Autograder Lab Splendid Synchronization Synchronized!

We have released the Splendid Synchronization AG! Please note this ag will take much longer time than the other ag. It t
- An instructor thinks this is a good note
2/26/17

2
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sbrk returns -1

If sbrk returns -1 does that necessarily mean I requested for too much memory, or could there be other reason?
2/26/17

2
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strange seg fault

I have the following lines in my free() if(fall != NULL) if(fall->is_free) when fall is a metadata struct pointe
2/26/17

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malloc

void *malloc(size_t size) { 09 10 /* See if we have free space of enough size. */ 11 metadata_entry_t *p = head; 12 meta
2/26/17

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Exec failed Mcontest

When I typed in: ./mcontest testers.exe/tester-1 I got the following output: exec() failed: No such file or directory
2/26/17

13
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SIGKILL

Whenever I run tester 4, I get the Signal 9 for why it failed. This is SigKill. Is there anyway for me to find why this
- 1 Unresolved Followup
2/26/17

4
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Tester-5 Purpose

Hi, So I am passing tests 1-4, but on the 5th one I segfault. I'm assuming this is because of an edge case that I
- 1 Unresolved Followup
2/26/17

3
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Failing Test 6

I'm failing only test 6 so far. The test looks like it covers reallocating into smaller sizes and then allocating so
2/26/17

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Splendid AG

When will Splendid ag start running ?
2/26/17

17
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Sbrk

I have: meta_data* ret = sbrk(size + sizeof(meta_data)); allocating memory for me. However, on test 4, the second ti
2/26/17

2
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Passing tests but not on AG?

I pass the first 9 test cases when I run the testers, but on the autograder I failed for test 5. Any idea why? Aren'
- 1 Unresolved Followup
2/26/17

2
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failed test 2,5,9

always failed with these three tests, ("Sending a SIGTERM to kill the child process (pid=13624) for running for over
2/26/17

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Memory outside heap

For Test #4, I always get: Data allocated outside of heap. Calloc/Malloc/Realloc returns a ptr: 0x321fa4d69. Your heap s

▾ Week 2/19 - 2/25

2/25/17

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best way to debug an error of Calloc/Malloc/Realloc returns a ptr: (nil).

I'm getting the error specified above in some of my test cases but I'm not sure how to actually find the call to
2/25/17

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Initial heap size

I am confused where to start in my malloc function. I understand that I need to keep track of how much data is free or a
2/25/17

2
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What am I doing wrong test 1

If i implement my malloc and not the free I actually pass the test. But if I implement my free all I do is check if the
2/25/17

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Topics?

What topics/lectures are going to be covered on the first midterm?
2/25/17

6
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Malloc doesn't run?

I am passing test cases 1-3 and I just finished my realloc and when I run test case 4 it doesn't even run? It automa
2/25/17

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MContest vs MReplace

My implementation segfaults when I try to run ./mcontest /bin/ls. However, when I run ./mreplace /bin/ls, everything wor
- 1 Unresolved Followup
2/25/17

4
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tips for faster malloc? (tester 5)

Edit: Thanks guys! I just wrote some code that optimised itself so it works now (I did see @1419 !) I currently tak
2/25/17

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debug malloc

I had seg fault in my code and when I run gdb --args ./mreplace testers_exe/tester-2 and try to step into char **env =
2/25/17

2
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Interpreting the tester output

For each test, is it sufficient to just see 'STATUS: OK'? Or do we also need to see the 'Memory was allocate
2/25/17

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Bookkeeping in malloc

In the book, we suppose to use a 2-byte word to restore the length of the block. I wonder if 15 bits (16-1bit) is good e
2/25/17

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What do 'MAX' and 'AVG' mean?

I looked at mcontest.c but couldn't find much about about what they could mean. The problem is regardless of which t
2/25/17

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Buddy Allocator

I just have a few conceptual questions about buddy allocators. I've been doing a lot of reading and haven't fou
2/25/17

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Failed test locally on VM but passed in AG

I ran test 3 on my local VM and it seg-faulted and failed. However, my AG tells me that i pass test 3. How should I thin
2/25/17

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Test 4 Timeout

I keep failing to produce an approach that passes test 4. I pass all other tests, but for some reason I cannot pass this
2/24/17

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what is signal 9?

Cannot find any information online
2/24/17

3
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sbrk question

1. metadata* newdata = sbrk(sizeof(metadata)); newdata -> payload = sbrk(size); 2. metadata* newdata = sbrk(siz
2/24/17

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pointer aligning

are we gonna be tested on pointer alignment in other words, do we have to align them so that each address of the allocat
2/24/17

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Citing Code

Could we use a short 15 line sorting algorithm for a doubly linked list we found on the internet if we cite it?
2/24/17

4
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how to split heap?

Say I need to allocate a new piece of memory with size of n; And I found a node "a" in my metadata with availabl
2/24/17

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codes from class

Is the corrected code from lecture posted somewhere? Update: found it
- 1 Unresolved Followup
2/24/17

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How to start?

Hi, I am kind of confused on how the memory allocation actually begins the first time someone will call our malloc. So I
2/24/17

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rendezvous_sol.c never destroys its semaphores

I know it isn't graded, but I was just wondering what the consequences are for not destroying semaphores... a memory
2/24/17

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Instr ICSS

Here is flyer about the ICSSP program that they presented about in class today. ICSSP_Flyer_with_deadline.pdf
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2/24/17

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what is the point of the practice midterm?

just to test how much we'll get? would we even be able to review what we get wrong at home?
2/24/17

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brk and sbrk

I want to make sure my reasoning is correctly. We use sbrk to allocate new memory assuming there isn't already space
2/24/17

1
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Instr Saturday OH 10-12 Cancellation

Hi all, Apologies for the inconvenience. I will be moving my Saturday office hours from 10-12 to a day next week that I
2/24/17

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Lecture Song Request

Ed Sheeran - Shape of You
2/24/17

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just to be clear

if we pass tests 1-6 locally, we should get 100% on the autograder tonight, correct?
2/24/17

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Instr Autograder MP Malloc Part1 Allocated!

AG for Malloc Part 1 is allocated! Schedule: "2017-02-24 22:00", "2017-02-25 22:00", "2017-02-26 22
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2/24/17

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Instr Friday 12-2pm OH cancellation

I apologize for the last minute cancellation. Woke up not feeling so well. I will make it up sometime next week. Good lu
2/24/17

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Is a TA coming?

Don't see anyone on the queue for 10-11 AM office hours today.
2/23/17

3
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how to debug segfault

I used the gdb to set the breakpoint before malloc (line 10 in test1) but the tread just exit, I can't go through
2/23/17

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Max and Avg

When I run the first three tests individually, both max and avg appear to be zero. However, when I run all the tests tog
2/23/17

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setting break point in gdb

I use the following command to use gdb gdb --args ./mreplace testers_exe/tester-1 When I try to set break point on my al
2/23/17

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Data allocated outside of heap

Does anyone know what the "Data allocated outside of heap" error means? The address I'm returning is 0x69b01
2/23/17

3
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undefined reference to main

I changed some things in my alloc.c and now I get this: what could've happened?
2/23/17

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./mreplace vs ./mcontest

Hi, When I run ./mcontest testers/tester-5, the program fails with code 91(Data allocated outside of heap.). But when ru
2/23/17

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Critical Section Problem

In the wikibook there was a proposed solution, duplicated below: https://github.com/angrave/SystemProgramming/wiki/Sync
- 1 Unresolved Followup
2/23/17

4
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How to download lecture videos

I'm going on a trip and I want to download the lecture videos, but when I click the download video file it only lets
2/23/17

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Tester 5

My malloc for test 5 takes too long and gets killed after 30 seconds. I've figured out that it takes forever to go t
2/23/17

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Prairielearn upload issue

I finished the practice exam, but when time ran out, Prairielearn didn't let me submit my code because time ran out
2/23/17

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Boundary tag question

If I implement a boundary tag at the end of every chunk I allocate so that I can go back to the metadata of the previous
2/23/17

2
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Malloc Week 1 Grader Clarification

To be clear, the performance tests are not a part of this week's grade for malloc, right? That would make it so that
2/23/17

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Instr "Malloc Realloced" - anon @1320

Dear students, We've deployed updates for Malloc to your SVN repositories. We update the error message so that you
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2/23/17

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Malloc auto grader?

When will the malloc auto grader run?
2/23/17

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Test 2 Times Out??

I'm passing test 1 and test 3 with excellent speediness but for some reason test 2 is timing out on me. Any suggesti
2/23/17

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PTHREAD_BARRIER_SERIAL_THREAD

Does our barrier implementation need to worry about returning the constant PTHREAD_BARRIER_SERIAL_THREAD to an arbitrary
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2/23/17

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Is the midterm autograded or handchecked?

For example in CS233 it was first auto graded and scores below 100 were hand checked. I was wondering if this course fol
- An instructor thinks this is a good question
2/23/17

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Instr Teaching Threads AG Final

Sorry everyone! We don't mean to worry you or delay your existing worry, but for various reasons the Teaching Thread
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2/23/17

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threads-ag

how long does it take for the AG to run/?
2/23/17

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tester 4 infinite execution time?

To my knowledge, there is not part of my realloc code that would run in an infinite loop, and furthermore, when I step o
2/23/17

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metadata struct

are we allowed to build and use a struct like metadata, like it was provided on the lab mini_valgrind
2/23/17

1
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Instr Splendid Synchronization Synchronized

We have released the Splendid Synchronization Lab!This lab is located in your SVN repo at: https://subversion.ews.illino
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2/22/17

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malloc

when I run gdb and try to check my memory, I got a result like this: (gdb) print a $4 = 0x603020 "\020" (gdb) x/
2/22/17

2
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GDB on Malloc

Can someone explain how to use GDB on malloc? The main function calls exec(), which throws off GDB, as far as I can tell
2/22/17

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My function is not returning anything

The final value in my function par_reduce is the right value, but it doesn't return anything to main even though I s
- 1 Unresolved Followup
2/22/17

2
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Local tests timing

When I test 1-13 locally, the times seem to vary very drastically for some of my cases. For instance, test 6 takes anywh
2/22/17

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Speed test

Failing speed tests. Basically after my threads exit and I have a final list of integer values, I call reduce on them fo
2/22/17

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malloc test output

Sometimes the test cases for malloc do not print out anything. They finish with STATUS:OK but do not print "Memory w
2/22/17

2
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task list

Do we need to use a loop to copy over the list into the task struct or is "task->list = list" fine?
2/22/17

9
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Memory Overlapping

Any help for this error message? I've tried debugging my code for a couple hours. Not sure how this can even happen
- 1 Unresolved Followup
2/22/17

4
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resolved

resolved
2/22/17

4
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perfomance contest

Is malloc the only function will be contested, or the performance of realloc and free will also be contested? Thanks.
2/22/17

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Failed 91 and 68

I'm getting a failed 91 and 68. There are explanations on the wiki of different error numbers, but not these 2.
2/22/17

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Why is the queue gone?

It says on the website that office hours go till 8 today. Was that changed?
2/22/17

1
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failing "doesn't evenly divided list"

I am currently failing both the short and long doesn't evenly divided test. But what I test on my own machine is per
2/22/17

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recalloc

Extra bonus points if we have a recalloc?
2/22/17

0
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free clarification

If the user passes an invalid value to free(), such as trying to free a pointer already freed or free an address in the
2/22/17

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returning value other than void*

For the helper function, the return value I'm using is void* but I'm storing the return value of reduce() in an
- 1 Unresolved Followup
2/22/17

1
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Lecture Music Request (3PM)

Earth Wind and Fire, The Four Seasons, and Brandy by the Looking Glass
2/22/17

3
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Question on Notes

I am looking at the notes Pthreads part 2 on the topic of race conditions. I type this below and see the error. #includ
- 2 Unresolved Followups
2/22/17

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base_case

I think that the way we used base_case in this problem is not correct...which is why I was losing points on multiple thr
2/22/17

2
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Modifying task struct

Are we allowed to change the task struct? I find it easier to implement the program if output is just an integer and not
2/22/17

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thread concept

what happens if the main thread finished before children threads wothout waiting them. (no pthread_exit nor pthread_joi
2/22/17

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Sources of Allocation Error

I've been having some really strange issues with my allocation/de-allocation techniques and I've been unable to
2/22/17

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"Speed Test"

I am not passing the speed test, but everything else runs. How should I debug that? I am using threads and after every
2/22/17

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Getting result

I'm not sure if I'm doing the thread correctly. When I do thread create in the helper function do I call reduce_
2/22/17

1
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How to deal with this?

My function finds start of index by dividing list_len / num_threads to do job. For example I have 6 elements and 3 threa
2/22/17

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will printing in my reduce_par.c affect the autograder?

Will it affect the autograder ?
2/22/17

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Exec Failed in MContest

As soon as I run ./mcontest 1 I get the error exec() failed: No such file or directory. I'm sure it probably has som
2/22/17

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Instr Teaching Threads AG Tests Swapped

Hello!We've noticed that a few of you have been passing Multiple Threads, Doesn't Evenly Divide Longer List and
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2/22/17

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Different output every time running long list test

When I run test like this ./par_reduce add 1500000 3 It seems that every time I run it, I got different output. Could it
2/21/17

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"One Thread, Long List"

I'm failing this test, "One Thread, Long List" (incorrect output) However when I test it, I can't find
2/21/17

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Max threads?

What is the max amount of threads we should be able to run? or does this depend on our computer?I thought maybe not sinc
2/21/17

2
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Changing Nicknames

Once the contest starts, will changing the nickname file change our nickname, or do we need to have it finalized by the
2/21/17

2
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Free function

Do we need to handle double free in our implementations?
2/21/17

2
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run reduce on the returned new list?

If there was eight threads then the new list i created would have eight elements right? would i just run reduce on all e
2/21/17

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Joining Threads

Right now I am essentially looping through and creating a certain number of threads and I am passing a helper function t
2/21/17

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A bit about VM

Hello, In order to optimize the malloc, I am wondering when VM accessing the memory, how many byte chunk is it
- An instructor thinks this is a good question
2/21/17

1
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Leaking memory if command is not found

If I run a command not found with valgrind, it doesn't run through my frees and leaks memory. Should we be handling
2/21/17

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how to we give unique ID's to multiple threads?

when we create a thread by using pthread_create, the first argument should be the id of the thread. When we create mul
2/21/17

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Debugging teaching_threads

Having troubles debugging my par_reduce. I used make debug, and then tried running gdb ./par_reduce-debug as well as so
2/21/17

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Little Poem I wrote for malloc

To be, or not to be? That is the question— Whether ’tis nobler in the mind to suffer The edge cases and memory tests of
2/21/17

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pthread_create void *(*start_routine) (void *)

When I'm passing in reduce_func it gives me an error : par_reduce.c:40:32: error: incompatible pointer types passing
2/21/17

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Grade Calculator - (In case Chara isn't updated quick enough for ya)

For those of you who like to keep track of your grade and Chara Grade isn't updated as quick as you'd like. Her
2/21/17

1
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Question About Task Struct

Here is the task struct provided to us: typedef struct { int *output; // Pointer to where the output should be
2/21/17

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Number of Test Cases: Clarification #Malloc

I'm a bit confused as to the number of tests we are going to be tested. I believed I read that Test 13 will not be t
- An instructor thinks this is a good question
2/21/17

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malloc test output

Test 10 running Exceeded Memory Limit (13421772800) [mcontest]: STATUS: FAILED=(68) [mcontest]: MAX: 13555994578 [mcont
2/21/17

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teaching_threads

I create my threads on the stack and if you send in 10 million threads and 10 integers I only create as many threads as
2/21/17

1
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Question on threads

If I set too many threads, for example, over than 100000, then I get a segfault. Is this normal or should I set somethin
2/21/17

0
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Casting

Is this the correct way to cast a void* to a struct*? I figured this was pretty trivial, but I can't seem to get th
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2/21/17

0
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What was the subtle bug that was causing kill zombies to fail?

Now that the MP is past due, I am curious what the bug mentioned in @1227 and @1282 was? It was a bug that was a
- An instructor thinks this is a good question
2/21/17

0
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Memory libraries

I'm confused as to what extent we are not allowed to use the libraries C has for memory. For instance, for calloc ar
2/21/17

1
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Instr Moving my OH forward

Dear all, I have to move my office hours forward for this week because of a workshop. So I'll hold my OH from 8:40-
2/21/17

6
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GDB Instructions Not Working?

The GDB instructions for debugging don't seem to be working on the malloc documentation. How do you use gdb? gdb -
2/21/17

3
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number of threads

when you count the thread, will you include the main thread. for example, there is a test called one thread, short list.
2/21/17

1
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Instr Office Hours Cancelled

Hey everyone, I'm cancelling my office hours this evening from 5 - 6 PM. I will hold additional office hours later
2/21/17

4
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start routine?

When the lab instruction says You should create a start routine for your threads. Does that mean we have to implement
2/21/17

2
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pthread stack variable

void start_threads() { int start = 42; void *result; pthread_t tid; pthread_create(&tid, 0, myfunc, &sta
2/20/17

0
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Resolved

Resolved
2/20/17

0
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Waitpid in handler always returns zero suddenly.

After the last autograder run I went back in to check my execution and suddenly my handler was no longer entering the wh
2/20/17

8
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Long list fail

I fail the "doesn't evenly divide longer list" test. Is there any way I can test it? "Longer" list i
2/20/17

1
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file_test

I have passed all file_tests for past several AG, but after the 9 pm one. I didn't pass the file_test any more but
2/20/17

3
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print_exec_failed leaking memory

when I have this print statement after exec failed, I am having a memory still reachable error. However, when I comment
2/20/17

2
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Exit test

I am still failing the exit test but I am not sure what exactly the correct exit code is supposed to be, right now I am
2/20/17

2
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Question on ps

Does the built-in ps have to register itself in the process vector and print itself out? The only way to do this would b
2/20/17

5
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Svn commit

Is there a way to check which commit the autograder ran on? And what my latest commit is? I may have committed something
2/20/17

3
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free_args not doing its job

I allocate memory to a char ** with strsplit at the beginning of my loop, and every time at the end I use free_args() on
- 2 Unresolved Followups
2/20/17

5
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Instr Malloc Redeploy

Dear students, We've deployed updates for Malloc to your SVN repositories. We update the error message for ptr out
- An instructor thinks this is a good note
2/20/17

7
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Not killing!

I don't get why my kill is returning -1 when I print out the return value of kill(). I print out the PID's throu
2/20/17

2
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Everytime I exit(0) the shell prints out "Terminated"

Is this normal? Will it affect that AG?
2/20/17

0
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debugging

is is possible to use GDB with commands like stop and cont ?? Thanks
2/20/17

0
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Failed to STOP process?

Does anyone know how the autograder determines if the stop program worked or not? I've been stuck on this for the pa
2/20/17

2
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background process

definitely run background process but AG says Failed to background process in office hour the TA says this one should p
2/20/17

2
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par_reduce is taking longer when run with more number of threads

I run par_reduce with 1 thread, it takes 0.000093 secs. i run it with 5 threads it take 0.000255 secs. Why might it be s
2/20/17

2
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End of file

When we're done reading from a file do we exit our shell or do we prompt for more input?
2/20/17

2
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When do we have to remove our process from the vector?

When it has done or when it got killed?
2/20/17

3
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AG update

Waiting for the AG scores to be up like C2UxB22WgAAlJRs.jpg
2/20/17

5
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Lengths that each thread deals with

Say we had an array of length 7 passed to par_reduce with 3 threads required. Does it matter how we divide the work? For
2/20/17

4
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ampersand

If & character is found anywhere in the command, it makes the process a background process. Therefore, making it im
2/20/17

11
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6 PM Autograder ????

Waiting in a state of panic right now When can we see the results?
2/20/17

2
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Prompt pid

From what I understand, if the shell executes a new external command, it creates a new process with a new pid. But, the
2/20/17

11
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clarification

I wonder will the AG gives us new format.c or it will keeps what our won is. I have this problem because that several da
2/20/17

4
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If number of threads are greater than the list length

Hello, Good evening. I have a question about the lab teaching_threads. I talked a course staff and was told th
2/20/17

7
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invalid command

when we loop through all the key world match if statement, and turns out that a command is nither a builtin nor extern,
2/20/17

5
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Things I've learned from shell.

In addition to all the coding things... it seems using shell has actually brought to my attention some things in linux.
- An instructor thinks this is a good note
2/20/17

2
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phd

fork bombed the AG received Ph.D. from isu
2/20/17

10
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cont not working

I'm getting a 4/6 on my stop cont kill test. The error says that my Kill command is not working properly, however I
2/20/17

1
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Strange output when running malloc test cases?

The output is STATUS:OK for all tests and the time output seems really strange. Can someone explain?
2/20/17

3
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Will there be class on Friday of the exam week?
2/20/17

4
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Currently running foreground process

In the docs it says to kill all running foreground process if the user presses ctrl-c. This does not make any sense to m
2/20/17

2
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process shell still existing after exit

Every time I exit my shell, instead of my child processes turn into zombies, my shell process still exist. I am sure tha
2/20/17

6
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invalid commands

I'm failing invalid commands... Do any of these print outs look weird to you guys? Please help! Thanks.
2/20/17

11
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Illegal instruction

edit* Hi, so I'm working on the lab, my code compiled, and when I try ./par_reduce add 20 4 I get Illegal instructi
2/20/17

6
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default memory leak

I'm leaking memory when I call my default constructor. My destructor void process_destructor(void* element) { free
2/20/17

2
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base case used in every thread?

In single thread, the base case is only used once, but when we use multi threads, the base case will be used multiple ti
2/20/17

1
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Instr Cancelling my OH tomorrow from 10-11AM

I'm afraid I won't be able to make it to my office hours from 10-11AM tomorrow. I'll try making up for the l
2/20/17

2
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% with EOF

When I start a shell and enter Control-D, my output looks like this before the shell exits: (pid=5013)/home/evankay2/cs
2/20/17

5
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exit codes

I am not passing the eof_test or exit_test because I am not passing the right code when I exit. Right now I pass exit(1)
2/20/17

11
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Cleanup_Zombie

I've been running tests with sleep in the background trying to create a zombie, but everytime they seem to be cleane
2/20/17

2
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print_command_executed for not found commands?

My shell prints out pid and command executed for commands not found like asdf I was wondering if this is correct behavio
2/20/17

2
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shell failed to kill

I succeed to kill on VM, but the autograder told me that it failed to kill. I'm not seeing why......
2/20/17

3
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invalid command

I attached my shell results of invalid commands here. I didn't find any leak when I run my shell, and also it pass
2/20/17

4
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does memory_check test valgrind errors?

I am getting a "Conditional jump or move depends on uninitialized value(s)" error that I haven't been able t
2/20/17

5
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waitpid on foreground process wait forever

I have a sigchld handler which waits for background process. I use while(waitpid(-1, status, 3options) in the handler fu
- 1 Unresolved Followup
2/20/17

1
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Failed only cd test, which passed before

My cd test passed before, but after I fixed a bug on eof test it failed. Now I passed other test cases except this one.
2/20/17

2
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Pass file test, but fail file test hard

Is anyone else having this problem? When i make test files and run, my shell runs just fine and even opens emacs properl
- 1 Unresolved Followup
2/20/17

0
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Malloc main leaking memory

I ran the first two tests, and each time I got this exact valgrind output: 272 bytes in 1 blocks are possibly lost in l
2/20/17

3
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I am really enjoying this MP

This MP stimulates my hippocampus! &
- An instructor thinks this is a good note
2/20/17

6
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Do we need to include main process to the vector process?

When doing ps using print_process_info, do we need to print out main process as well?
2/20/17

2
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Fails to kill...

I failed the built-in kill functionality. I ps'd current processes and it seems fine. I verified that the killed pr
2/20/17

2
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Does the midterm cover everything up to and including synchronization?

What sections of the Wikibook will be covered in the mid term?
2/20/17

8
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Background runs but still fails AG

My background functionality seems good. My background processes can be seen after calling ps, and they are actually func
- 1 Unresolved Followup
2/20/17

0
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Malloc mp

Shows the following whenever I test now after testing the exact same code continuously. Data allocated outside of heap.
2/20/17

3
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Printing to stdout for file output

In the documentation it says: You should not be printing out to stdout and stderr at all But it also says when we exec
2/20/17

11
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shett

I wrote over 350 lines of code and still getting 7/23...
2/19/17

3
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strcmp literal for Shell Internal Commands

I'm trying to figure out whether or not I have to call an internal command (like cd, ps) using if statements and str
2/19/17

8
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Passing hard mem but failing easy mem

Is anyone having this problem? If so, do you have a general thing that you ran/checked for, fixed it, then got full cred
2/19/17

4
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Why am I failing file_test?

I don't understand how I am failing file_test when I am passing file_test_hard and file_test_hard2. I tested running
- 1 Unresolved Followup
2/19/17

26
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Is this a normal behavior?

When I try to type an invalid command in the shell it still says the Command is executed by pid = ____ and then it say
2/19/17

2
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invalid command and memory

I attached my shell results of invalid commands here. I didn't find any leak when I run my shell, and also it passe
2/19/17

2
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ctrl D on empty line

when I do sleep 60 on foreground, should ctrl D exit the program ? since now, only ctrl C can be caught to terminates th
2/19/17

2
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Exit Status

When should the exit status of the entire program be 1? The docs state that the program should exit with status 1 on fai
2/19/17

3
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pressing enter in shell

when I press enter in my shell without any command, it segfaults. I am planning to add a condition of 'no input
2/19/17

2
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Echo Hello

When I type echo hello into my shell, it reads the line as "echo hello\n", so it prints out an extra line. Shoul
2/19/17

4
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Keeping track of background process

I understand that when an & is given after an external command we should run the command and not wait for it to fini
2/19/17

5
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when we run with -f

\ When we run the file command, are we supposed to get out of it after all commands are executed as above?
2/19/17

4
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SIGTERM vs. SIGKILL

Should we send SIGKILL to a stopped process if the user calls kill on it? It seems that a stopped process can't be k
2/19/17

6
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Totally lost with using process vectors

The documentation says Your shell should keep track of the name, PID and status of every child, it creates. You might
2/19/17

0
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failing cleanup_zombies: Process failed to run in background

When I test my code I successfully run processes in background (pid=8626)/home/shell$ sleep 10 & Command executed by
- 1 Unresolved Followup
2/19/17

3
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How to execute several command sequentially in one process?

Kind of stuck in here... If we do fork-exec-wait, how can we let all the command executing in the same process,...
- 1 Unresolved Followup
2/19/17

2
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After EOF detected

I saw another post saying it is fine to print the last line of prompt before exiting, but do we need a new line after th
2/19/17

6
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cd output

My shell executes cd just fine; however, there is no newline printed after it finishes, so my output looks as follows: (
2/19/17

4
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kill question

1. Are we supposed to implement the 'ps' before we do the kill ? 2. on the documentation, it says kill <pid
2/19/17

2
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Instr Malloc Allocated!

Malloc Released! Malloc has been released. If you svn up you should see it. This can be a very, very fun MP if you star
- An instructor thinks this is a good note
2/19/17

3
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EOF Test

I'm failing EOF test and trying to debug the issue. If I remove the newline char from the last line of my script us
2/19/17

3
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CTRL+C

Is ignoring CTRL+C only considered when dealing with stdin, or also for files? If we also need to handle it for a fi
2/19/17

4
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Segfaulting at strsplit()

Hello. I am extremely confused as to why I am segfaulting at my call to strsplit. This is what I am running that causes
2/19/17

2
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Command names for PS?

For ps and just in general, should the command be something like "sleep 20", "sleep 20&", or would t
2/19/17

0
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Creating vector shared by parent and children

Right now, every time I call my vector to push a new processes after forking, the child process created a new vector. Ho
2/19/17

23
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Instr Autograder MP Shell Update

Dear 241 Students, We made some updates on MP Shell AG. From now on, we will run the AG every 3 hours. Remember, if y
- An instructor thinks this is a good note
2/19/17

3
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Tips on how to find zombies?

I'm currently failing cleanup_zombie, so I'm testing my shell by having top -c running in another terminal and t
2/19/17

5
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Cleanup with status

void cleanup(int signal) { int status; while (waitpid((pid_t) (-1), 0, WNOHANG) > 0) {} } This is the cleanup exa
2/19/17

4
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Check the pid of a background child

I want to remove a process from my vector after it has exited, but how do i get the pid of a background child that has e
- 1 Unresolved Followup
2/19/17

0
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Need some clarify

I see that the doc has been changed. It is important to note that, upon a successful execution of the command, exec()
2/19/17

3
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cd no directory

i have the code: printf("%s\n", cwd); err = chdir(cwd); if(err == -1) print_no_directory(cwd); and my terminal
2/19/17

2
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SIGCHLD handler

I looked up man page but I am still not sure if I get this code(from wiki) correctly void cleanup(int signal) { int s
2/19/17

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Exec example

Why isn't hello printed out after each of the integers? I thought about output being buffered, but I am not sure how
2/19/17

4
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exec Failed

In the wikibook's example, I understand that echo is spelled incorrectly, therefore causing exec to fail. However ho
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2/19/17

16
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Program Timeout

I got "timeout" in "background" test and "stop cont kill". What does "time out" mean? I
- 1 Unresolved Followup
2/19/17

0
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Increasing the Heap

Why does sbrk return a higher address when the heap is suppose to grow upward?
2/19/17

4
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file output format

./shell -f commands.txt <---- DO WE NEED TO PRINT THIS LINE? (pid=1234)/home/user$ cd cs241 (pid=1234)/home/user/cs2
2/19/17

3
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Failing Memory Tests Now

Prior to the AG going down, I had a 23/23 on the tests. Checking now, my grades dropped to 17/23 failing both of the mem
2/19/17

3
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Does SIGINT need to create a newline, like it does in a real shell?

$^C$^C$ or is it acceptable if our shell would do the following given two SIGINTs? $^C^C I.e. do we need to reprompt the
2/19/17

7
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Sending SIGSTOP to a process (sleep)

So I passed the 4PM signal test but failed last night's... Failed to STOP a process. I'm seeing some strange beh
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2/19/17

7
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child exec failed

so if in the child process exec failed, should I always exit(1) afterwards? or the child process will never end?(except
2/19/17

5
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getting pid of a background process after exiting

I am having a signal handler to handle SIGCHLD in case that a process in background finished and becomes a zombie. Howev
2/19/17

5
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Reading from file and stdin

When the shell runs, do we need to consider the situation that the user first enters few commands via stdin, and then us
2/19/17

2
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Unable to kill child process

When I sending SIGTERM to my child process, sometimes it works and 0 is returned, but most time it doesn't and -1 is
2/19/17

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Parent seems to be waiting forever when calling stop on a child

When I did something like this (pid=31513)/home/user/cs241/shell$ ps Running 31513 ./shell (pid=31513)/home/user/cs241/s
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2/19/17

3
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What to do when kill/stop/cont is ran without a pid?

Just to make sure, In the documentation, it says Use the appropriate prints from format.h for: kill was ran without a p
2/19/17

9
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Failing Kill Test

I'm getting "Failed to KILL process" on my stop_cont_kill_test but as far as I can tell from my tests it wor
2/19/17

2
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Kill

I am trying to call kill(pid, SIGTERM) when someone types in the kill command, but I am getting the following error when
2/19/17

2
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Instr Shell AG Run Completed!

Dear students, The Shell AG has been completed! If your code fork bombs on any autograde, then you will automatically
2/19/17

2
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in my sigchld handler, waitpid always return -1

everytime my sigchld handler is invoked. my waitpid always return -1. I tried to print the errno. it said no child proce
2/19/17

6
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ps and kill clarification

for ps, are we supposed to get the output something that exactly looks like the output of ps in the real terminal? als
2/19/17

2
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Office Hours

Does Professor Evans hold office hours?

▾ Week 2/12 - 2/18

2/18/17

12
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Instr Autograder MP Shell is down

Dear 241 Students, AG MP Shell is down. We are looking into it. Another AG run will be announced later after we fix it.
2/18/17

14
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chdir command not actually working

I am currently working on my cd command and I wanted to test if my chdir is working correctly because my cd command did
- 1 Unresolved Followup
2/18/17

2
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If both child and the parent share filehandlers, why call fclose on both?

According to the wiki, and the man page, regardless of where you make changes to the file handles, they affect both chil
2/18/17

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"still reachable" bytes when input command is invalid

My shell does not leak memory or have memory error at the end of its execution (ie after exit), but when I call an inval
2/18/17

2
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cleanup signal

When I use SIGINT to clean up all child processes, I constantly failed to kill the processes thus failing to exit. When
2/18/17

5
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Kill (defunct process)?

When I killed the process running sleep 20 in the background, is it OK if ps shows the process as defunct?
- 1 Unresolved Followup
2/18/17

4
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-f

if -f is specified, should the prompt still be printed?
2/18/17

2
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Error Creating Thread

What should out program do if we get a non-zero response from `pthread_create`? Exit with a non-zero exit value?
2/18/17

2
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vector status clarification

Just looking for some clarification on the process vector: Do we remove a process from the vector when a process is fin
2/18/17

11
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shell format question

In The doc (pid=1234)/home/user$ kill blahblah 12345 Command executed by pid=1235 invalid_command: kill blahblah 12345 (
2/18/17

20
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Clarification on ps

Can someone clarify what should the output for ps be? Is the following a valid one? (pid=21683)/home/user/cs241/shell$ c
2/18/17

3
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Casting to pid_t

In shell.c, I turn each line of the file into a string. (and I turn these strings into strings themselves) However, when
2/18/17

2
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Do we need to print after child finish execution

I understand that we need to remove child process from vector after it finish execution, but do we consider this behavio
2/18/17

10
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what are background/foreground processes

So I've done some reading, but I still don't know how to handle background processes, should it also be in the p
2/18/17

16
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default shell run with ./shell

Hello. I was totally lost but trying to get somewhere by slowly following the documentation. And I need some more guide
- 1 Unresolved Followup
2/18/17

7
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STOP, CONT, and KILL

How does this new test work? I got the error of timeout. Tell me if I misunderstand anything. Here's my understandin
2/18/17

9
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Can shell kill itself?

can i call kill <pid> on the shell's pid?
2/18/17

4
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stop also trigger SIGCHLD

Found out that send SIGSTOP will also let child send SIGCHLD to the parents, and parents can not distinguish whether it
2/18/17

5
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zombie child

Does the parent process need to wait for the child immediately after it calls fork? Say the parent process has following
2/18/17

2
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Old quizzes?

Is there any way we can review old quizzes/practice midterms in order to study for exams?
2/18/17

3
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WIFEXITED vs waitpid = -1

Are these different? would wait failing mean the process exited with a non-zero status? in other words should we print_w
2/18/17

2
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Signal handler with process vector

After doing some searching I know you can't pass additional arguments into signal handlers, but we need some way to
2/18/17

2
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Kill with pid containing letters

Should we print out invalid command for a call to kill with letters inside of the pid or should we print out process not
2/18/17

3
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invalid pointer when calling vector_destroy

I have a global vector of processes that I use to keep track of processes. For my cleanup at the end of the program, I c
2/18/17

6
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should I prompt when start ./shell?

So when you prompt, you should print the current pid where the command is going to run right? so when I first start shel
- 1 Unresolved Followup
2/18/17

2
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Catching SIGCHILD and Cleaning Up

I've been cleaning up processes based off of the PID. If there are multiple processes running concurrently, how do I
2/18/17

2
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Vector of Processes

I defined the vector and wrote the callback processes but whenever I try to access the the vector I get the error: shell
2/18/17

7
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shell clarification

So there are only two ways to run the command in the shell mp and they are ./shell -f filename.txt and ./shell <b
2/18/17

6
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Instr Shell AG Update

We are running an extra shell autograder this afternoon at 4 PM, because of a new unit test. The rest of the schedule re
- An instructor thinks this is a good note
2/18/17

2
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signal handling specifics

If you ask us to stop a function that has already been stopped or continue a function that is already running should we
2/18/17

4
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What to print when exec fails?

Suppose I tried to run the command "what on earth" with exec. This will probably fail; should I print "what:
2/18/17

6
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sigchild and waitpid

I don't know if I understand this two correctly: so if a child exit(killed), parent will receive a sigchild indicate
2/18/17

4
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Process struct

Are we allowed to change up the process struct? Say, if I wanted to change it to a linked list :0
2/18/17

3
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Topics covered in this quiz?

Do we have to go through threads or is it until the lecture covering memory allocators 2
2/18/17

2
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exec time fails but no other call I can think of does

ls, sleep, make, env, etc. all work, but for some reason time doesn't. Any reason this might happen? Thanks!
2/18/17

10
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failing eof

I am failing the eof test, but am unsure why. So far as I can tell from the docs, the only two times this applies is whe
2/18/17

2
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Something wrong with the Autograder

Is there anything wrong with the AG? Yesterday, I got a 11 points, and passed everything except the memory. However, I h
2/18/17

4
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vector_push_back invokes destructor

Hello, I was working on the shell mp and I found that whenever I call vector_push_back, the destructor I defined
2/18/17

4
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How to set a vector of processes

In the documentation, we are advised to create a vector of processes. How can we create such a vector given that there a
2/18/17

9
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shell mp question

Hi. I started this MP yesterday and I read all the required readings on the wiki. But I still don't get how I am su
2/17/17

4
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Vector to store string

I created a char pointer vector: vector *commands = vector_create(*char_copy_constructor, char_destructor, *char_default
2/17/17

6
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Understanding Shallow vector (pass null to vector_create)

I'm having trouble understanding this. When I tried to write callbacks, I had a whole mess of errors because it did
2/17/17

0
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memory_check test - does not depend on functionality?

Can we get any insight into what memory_check does if it doesn't depend on shell functionality? Does it start our sh
- An instructor thinks this is a good question
2/17/17

2
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check_background_processes

I am failing this test, but my code seems to work for background processes (ie i do sleep 20& and then type ls and t
2/17/17

3
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kill command failure output?

The shell docs say to use the appropriate prints from format.h when kill successfully sends SIGTERM, SIGSTOP, or SIGCONT
2/17/17

2
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External command kill on course webpage

The following is listed as an example on the webpage under the external commands section: (pid=1234)/home/user$ kill bl
2/17/17

3
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Share memory between parent and children

Do we need to share the vector which stores information of all process? I wonder how to share memory between parent and
2/17/17

2
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when to set a process to "stopped"

Should we shit a child's status to "stopped" in our process vector right after a parent finishes waiting? Wo
2/17/17

3
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"command" clarification

Does the word "command" in the doc include arguments? For example, if exec'ing sleep 1 failed, should we cal
2/17/17

2
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Should our implementation of kill be able to kill processes not tracked in our vector?
2/17/17

3
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invalid input?

Should we anticipate a case where there is invalid input and if so, should we provide a response? (e.g. "command not
2/17/17

3
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strtol use

I'm trying to use strtol to parse a user's input for a pid: (where path is a char*) pid_t pid = strtol(&pat
2/17/17

4
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Exit and EOF test

My grade report said Program did not exit with correct code. According to doc, “you should kill and cleanup each of t
2/17/17

3
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No TA

Office hour is open but there is no TA
2/17/17

7
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Failed cd test

I wonder why I failed cd test. I tried cd includes (path without “/“) and cd /home (absolute path). I also tried invali
2/17/17

2
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writing callbacks

Would it be naive to imitate the callbacks defined in callbacks.h if we write some for processes due to the presence of
2/17/17

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Shell with -f question

Is it correct to assume that calling shell as such ./shell -f would make a print_usage() call and not a print_script_fi
2/17/17

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background external commands

What is the status in struct process? Is it the argument in the wait function like wait(&status)? If it is true, for
2/17/17

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if exec fails, do we need to free all memory in child process?

If exec fails, do we need to free all memory in child process? This would be a pain because I'd have to pass all of
2/17/17

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Implementing ps

I did some searching and thought there is no library function or system call could help us to implement ps. It seems lik
2/17/17

1
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cd usuage

I understand that cd is supposed to change the current directory of the program but what are we supposed to change it to
2/17/17

0
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How to avoid the child being killed by ctrl c

Hi everyone. I search for the information about ctrl+c. Ctrl+c send SIGINT to all the foreground processes. So d
2/17/17

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What should the process command be after EOF?

If we start ./shell -f <filepath>, the process struct for shell should have the command "shell -f <filepath
2/17/17

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print_exec_failed clarification

Are we calling this function when the call exec() fails (i.e. fails to replace the process image and lets us proceed to
2/17/17

2
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Reading empty file

So if I read an empty file into my shell, like: ./shell -f empty_file.txt I print the prompt (without a newline charact
2/17/17

0
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CTRL-C

If there are stopped processes in the background, would we have to kill those when we catch ctrl-c or only the ones that
2/16/17

0
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Immediately Running Background Process Error?

So, on the newly deployed AG for shell, I am now failing the "check_background_process" test with the error: Er
2/16/17

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Shell mem_check

In shell autograder, the testcase memory_check has description : Memory test - does not depend on shell functionality. W
2/16/17

0
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cd ..

For cd as a built in command do we have to support the function's shorthand? If the input is "cd .." would w
2/16/17

4
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Instr Additional AG Run for MP Shell at 23:59:59 tonight

Dear CS241 Students, As some of you have noticed, the AG for MP Shell didn't run correctly at 22:00:00. We have rer
- An instructor thinks this is a good note
2/16/17

0
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AG Compilation Error

Trying to compile your code... FAILED TO COMPILE! /usr/bin/ld: cannot find -lprovided clang: error: linker command fail
- An instructor thinks this is a good question
2/16/17

0
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what happens after wait fails?

If wait fails, do we quit the shell once we print the error message? Since it doesn't quite make sense to "wait
- An instructor thinks this is a good question
2/16/17

6
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Do we consider & in file?

& in file should also be considered, right? ... or not...
2/16/17

1
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Instr Text Editor Feedback

Thank you all for your feedback! Please fill them out for upcoming assignments/ past assignments as well here : https://
- An instructor thinks this is a good note
2/16/17

2
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Instr Utilities Unleashed Feedback

Thank you for your feedback on this assignment! Please continue providing feedback on future assignments: https://goo.gl
- An instructor thinks this is a good note
2/16/17

1
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Shell file output

My output when executing a script looks like: Finished! (pid=1604)/home/mynetid/cs241$(Reads EOF, then exits) Should we
2/16/17

1
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exec free heap memory?

When exec is called in a child process, does it automatically free the heap memory inherited from its parent?
2/16/17

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When does wait fail?

I notice there’s a function called print_wait_failed() in vector.h. I wonder in which situation when wait fails? FYI, I
2/16/17

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wiki vs man page

http://man7.org/linux/man-pages/man7/signal.7.html man7 says that both SIGKILL and SIGSTOP cannot be caught, while wiki
2/16/17

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callbacks for process for vector

Another post mentioned if we needed to provide constructor etc. for process. Can we just define them outside main in she
2/16/17

1
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echo not found?

When I was trying out the external commands, /bin/ls worked, but echo was not found. Why is that? Edit: Nevermind we
2/16/17

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Use strstr() with mutable input (haystack) string?

I'm trying to use the strstr() function to parse the user's input for the commands' keywords our shell will
2/16/17

3
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Segfault for thread number >= 27

Is it normal for the program to have seg fault when num_threads >= 27 (works for all cases below it)? If so, is it b
2/16/17

5
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Instr Shell and Teaching Threads Redeployed

Dear students, We've deployed updates for Shell and Teaching Threads to your SVN repositories. For Shell, the provi
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2/16/17

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Instr Autograder Lab teaching_threads Released!

AG Teaching Threads is released. Schedule: "2017-02-17 22:00", "2017-02-19 22:00", "2017-02-20 22
- An instructor thinks this is a good note
2/16/17

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Memory Leak - Process Default Constructor

When I use vector_push_back to add a process to the vector of processes, I get a memory leak that originates from the pr
2/16/17

2
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make debug error

I can use command "make", however when I type in "make debug", there is a make debug error. rm -rf par_r
- An instructor thinks this is a good question
2/16/17

2
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num_threads > list_len

If the number of requested threads is greater than the number of elements in the array, is it acceptable to cap num_thre
2/16/17

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Built in command + &

What should we do if the input is Built in command + &? Should we just ignore the '&'? Or should we
2/16/17

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getopt question

so the man page says it returns a char, but it is an int returning function. This is the int form of the char, correct?
2/16/17

3
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Instr Teaching Threads Detangled!

We have released the Teaching Threads Lab!This mp is located in your SVN repo at: https://subversion.ews.illinois.edu/sv
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2/15/17

0
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How do i check that calloc zero'd out memory if I didnt use calloc in mini calloc?

I am not sure how to make the comparison without the compiler throwing an error for comparison. I tried casting to an in
2/15/17

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Vector of Processes

We are suggested to use a vector to keep a record of all running processes. Does that mean we will have to define our ow
2/15/17

2
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Storing struct in vector

How can we store struct process in vector? It seems like we can only store the primitive types using functions like int_
2/15/17

0
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Checking differences between SVN revisions

Is there a way to check the difference between two svn commits?
2/15/17

0
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ps clarification

Does our ps only print the information about our shell and the children of our shell?
2/15/17

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Understanding of Shell MP

So, for my understanding, there are several things to do for this mp. First of all, we have to know whether we read from
2/15/17

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Double free

If you realloc(pointer, 0) and then free that pointer does it count as a double free? I am getting a double free if I re
2/15/17

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Freeing a pointer to metadata?

If I'm using a pointer to point to the meta_data of memory, how can I use it to free the meta_data it points to? Cu
2/15/17

5
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Realloc Clarification & pointer arithmetic

Alright 2 questions here: - The void pointer ptr being passed to mini_realloc() is it ptr2 correct? (since thats what m
2/15/17

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freeing a NULL pointer

Let's say we have: void *ptr1 = malloc(10); free(ptr1); ptr1 = realloc(ptr1, 30); // Invalid Address, returns
2/15/17

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free ptr that's called by realloc

Hello! I am having trouble with this question char *p1 = malloc(10);char *p2 = realloc(p1, 20);free(p1); I think this is
2/15/17

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Weird edge case

When I realloc something to a bigger size it works fine. I can then even realloc this to something smaller. However, whe
2/15/17

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Question about total_memory_requested in realloc

When we call realloc and the request_size is greater than the previous allocation request_size, should we increase the t
2/15/17

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Memory leak in provided vector library

It looks like the implementation of vector provided with the shell MP will leak memory. When I compile and run the follo
2/15/17

5
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Calloc

I am unsure if we are suppose to allocate memory for the meta_data AND the requested size in calloc. I wrote this: met
2/15/17

5
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invalid pointer

in my test case i have void *p1 = malloc(30); void *p2 = NULL; p2 = realloc(p1, 50); I then get an invalid pointer erro
2/15/17

5
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Docs for Shell

I'm confused. The .h files included are practically blank and I don't see any description of specific functions
- An instructor thinks this is a good question
2/15/17

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Pointer casting order of operations

To return the blok associated with a meta_data, is it safe to do the following: void* retptr = (void*) meta_ptr + 1;
2/15/17

2
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Shell: background process when reading from file

If a file of commands specified with the -f flag contains a command that should be run in the background (for instance,
2/15/17

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ps with arguments?

What are we supposed to do if "ps" is run with arguments? Should we still do the ps command, or should we do not
2/15/17

6
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Question about "storing memory requested"

For mini-valgrind, should we need to add all memory requested in "total_memory_requested" or only the memory bei
2/15/17

4
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invalid bad free count

I've gotten a 2/6 on my autograder for the last 3 runs even though I've been working on it and was convinced I h
2/15/17

4
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Helper functions for insert meta data and remove meta data

If we make helper functions to help insert and remove meta tada from the list. do we define them and add them to mini_va
2/15/17

6
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Bad_Free

Currently failing the bad_free test case. I am passing every other test case. I was wondering when a bad_call to free wo
2/15/17

2
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No handouts?

The past few lectures I've been to at 3 PM there have been no available handouts. Did they run out or are there goin
2/15/17

4
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Instr Autograder MP Shell Released!

AG is running for Shell. If your code fork bombs on any autograde, then you will automatically fail this MP. Please ma
- An instructor thinks this is a good note
2/15/17

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Stopping Shell from Within Itself

I tried stopping my shell from within the shell itself. This brought me back to my regular command line, as I expected.
2/15/17

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Is it an issue if pids are not sequential?

Does this indicate that I am not properly cleaning up pids or is it okay?
2/15/17

4
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Can I call malloc and then realloc in the same function?

Or does that count as calling malloc/calloc/realloc multiple times?
2/15/17

4
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when to increment invalid address/calloc zero'd

Do we only increment invalid_addresses when we fail realloc and free? Also, for calloc it's telling me in my test ca
2/15/17

3
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mini_realloc clarification

There is a possibility that when realloc is called, a new block of memory is returned and the original block is freed by
2/15/17

2
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Testcases

I checked my lab grade and I passed the full test but failed the others. I'm confused because this means my code pro
2/15/17

2
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failing leak

I am failing the testcase of leak and passing others. It says that Incorrect number of leaks Does that mean that the le
2/15/17

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Invalid command format

If we run the invalid command: invalid_command --flag-that-is-ignored also_ignored also_ignored the expected error messa
2/15/17

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Killing a stopped process

What should happen if we call kill on a stopped process? I would expect that the desired behaviour would be to make sur
- An instructor thinks this is a good question
2/15/17

2
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Clarification on free()

is payload pointing to the memory block or is it pointing to the meta_data structure that comes before the memory block?
2/15/17

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Does it Matter where Shell Starts?

Can we start our shell in any directory, or does it have to be in the current directory?
2/15/17

2
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Testing calloc

I am trying to think of some ways to test and debug calloc.. When I test it, it seems to work fine. But I don't pass
2/15/17

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wikibook: Process

In wikibook Processes Part1 the image of memory has a section "libraries" in it. I am curious about this sectio
2/15/17

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" invalid next size "

what does this mean? *** Error in `./test': free(): invalid next size (fast): 0x0000000001bff890 ***
2/15/17

2
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increase total_memory_requested and total freed

If we realloc from 5 bytes to 10 bytes should we be increasing total_memory_requested by 5? If we realloc from 18 bytes
2/14/17

4
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realloc

I pass all tests except reallco. My AG told me I fail that because of Incorrect bad free count. However, I have passed b
2/14/17

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checking param payload

To check if it is a valid ptr, is it safe to cast metadata items in our list to void ptrs and offset them the same way w
2/14/17

3
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output test

I tried to call free but it outputs illegal instruction, what does it actually mean?
2/14/17

6
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realloc invalid ptr

If the user tries to realloc an invalid pointer, increment invalid_addresses and return NULL. so im not clear what it me
2/14/17

3
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The question about extra free

I don't know why, but it seems that the system is calling an extra free for me. For instance, if I have p1, p2, p3 c
2/14/17

4
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Lab Autograder

Do all the test cases call our implementation of free?
2/14/17

2
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Memset

Are we allowed to use memset with mini_calloc()?
2/14/17

3
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Calling calloc/malloc/realloc only once

So if my mini_realloc calls mini_malloc and return and in another way calling system realloc and return, which of two pa
2/14/17

2
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Realloc head pointer

If I realloc, do I have to point the head pointer at the realloc'd data, or can I leave the meta_data in place by up
2/14/17

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realloc question

I am kind of lost. So for realloc, we have to make the payload pointer to point to the newly allocated data with the n
2/14/17

1
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Instr Moving my office hour

Hi all,I have to move my office hr to Friday morning 9-11 AM this week only. Sorry for any inconveniences.
2/14/17

10
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free error

So in my malloc I malloc enough size for the meta data and the requested size, then I return a pointer to only the reque
2/14/17

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gdb on mini valgrind?

I followed the exact instructions from a previous post, but I still got the error messages: Make breakpoint pending on
2/14/17

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is calling free in mini_realloc ok?

^^
2/14/17

5
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Inserting at head

A friend and I were having a discussion on where we should insert a new malloc. The header file says "it creates a m
2/14/17

2
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Lab Attendance

Is Chara Gradebook now accounting for a lab drop?
2/14/17

4
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Realloc to size 0

In mini_realloc, if we realloc to size 0 (which means free the pointer), should we return payload or NULL? The documenta
2/14/17

2
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realloc idea

For my realloc function. am I supposed to create a new meta_data ptr and make the payload ptr point it to it first?
2/14/17

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test

why my test will print out leak size=0 at line 12? is that ok?
2/14/17

2
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Can we call free() in mini_free()?

The docs say we are allowed to call calloc() and malloc() in their respective mini_valgrind functions. But there is not
2/14/17

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Shell file structure

Will the file provided for the shell have commands in separate lines?
2/14/17

4
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Free after realloc

When I ran the following test case for realloc void *p1 = malloc(30);void *p2 = malloc(40);p1 = realloc(p1, 80);p2 = rea
2/14/17

2
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question about calloc

So I am kind of confused with the original calloc. It says it allocates memory for an array of 'n' elements of
2/14/17

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default realloc

for the default realloc, man page said it will return Null if failed. then, my question is , what will happen to the arr
2/14/17

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realloc

in the .h, "If the pointer is NULL and the size is 0, the behavior is * undefined." so for this case, we should
2/14/17

3
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Instr Please use your assigned VM

Dear students, We've noticed a few people have used VMs they were not assigned to. Please check the original messag
- An instructor thinks this is a good note
2/14/17

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func sig

i find that the func signature for realloc and free does not match, is that ok? between .c and .h
2/14/17

7
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Instr Text Editor AG Rerun

Dear 241 Students, We have rerun AG for MP Text Editor. You will receive max_score(deadline_run, this_run) on Chara. H
- An instructor thinks this is a good note
2/14/17

3
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Shell kill

In format.h, print for successful kill reads , void print_killed_process(int pid, char *command); How can shell get the
- An instructor thinks this is a good question
2/14/17

4
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Output if no directory provided for "cd"

I understand that no provided directory should be treated as an invalid directory, but print_no_drectory() requires an a
2/14/17

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Realloc Location

Hi, So if I call realloc on something, should it stay in the same place in my linked list? Or should I effectively delet
2/14/17

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mini_realloc: input payload

Do we always assume given ptr is at the beginning of the data block? what if the ptr is pointing to the middle of the da
2/14/17

2
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Instr Be careful about printf in Mini Valgrind

Hi students, I've seen a lot of people with this issue so far. Be careful with printf in Mini Valgrind! By default,
- An instructor thinks this is a good note
2/14/17

7
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total_memory_requested/freed

test: mini_hacks.c:380: void print_leak_info(): Assertion `total_leak == total_memory_requested - total_memory_freed
2/13/17

2
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last question

for display command, what if you cannot display max_lines (e.g. document_size = 9; handle_display_command(document, 5, 9
2/13/17

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payload in free is not the address I passed in

I allocate a 50 bytes characters array in the main fuction and try to free it. But the parameter in the free is not t
2/13/17

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cd with exec's

I've been unable to use the exec functions to execute cd. There is an "cd: not found" error. I saw some dis
2/13/17

4
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Displaying

When I run display with max_lines<doc size, it prints out the correct number of lines when I do ./editor_test. But wh
2/13/17

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Confused of index size

For our text editor, are we supposed make it so if the line goes above a specific index size, it automatically changes t
2/13/17

4
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Realloc implementation

In realloc, can we use either the C library realloc or implementing it using a combination of malloc and memcpy/memmove?
2/13/17

4
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editor weird display in terminal

In my terminal the display looks normal but once a line gets longer than the terminal window width and wraps around, ext
2/13/17

2
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Shell Process

Each process struct contains a command, status, and pid. For the shell process itself, is the command the initial comma
2/13/17

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Using Document_insert_line

I try to account for the case where insert wants to insert past the current size using Document_insert_line because said
2/13/17

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total_memory

In mini_realloc when we update global variables total_memory_requested and total_memory_freed, do we increment them by t
2/13/17

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Insert's importance

Next time a lot of test cases ride on a function like this, can you please make that clear in the next doc? A lot of peo
2/13/17

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Is it possible to zoom in and make the projected handout clear during lecture?

As above, that would really help
2/13/17

2
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Is it okay to reboot VM?

Just want to confirm that nothing catastrophic will happen if we sudo reboot the VM, and that VM will actually reboot in
2/13/17

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total_memory_requested

Should we only increase total_memory_requested when we are explicitly told to do so? I don't understand why we would
2/13/17

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Instr Bug In Final Lecture 2 Code

Well I have found the bug in the second lecture final code. The moral of the story is undo/redo can be messy. See if you
2/13/17

2
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What is the Deleted: 1 counter appearing at the bottom of my text editor.

It doesn't seem to be counting the number of deleted characters correctly even though my delete and backspace work
2/13/17

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Delete and Insert

This is more of a clarification question on exactly how delete works. Suppose I call this insert function as so handle_
2/13/17

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Insert_test

First of all, I failed insert_1 and two search. and I hvaen't implemented search yet by using editor, I typed Hello
2/13/17

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Shell Commands

Do we assume that commands passed into our shell are valid in terms of the number of arguments (except for the ones spec
2/13/17

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Insert NULL and search NULL

If i attempt to insert NULL, should the program crash or should the program simply return? How about when i try to searc
2/13/17

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When fixing insert fixes everything
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2/13/17

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shell optional argument -f

My understanding of the shell's optional argument: 1. the argument "-f <path_to_script>" is the only
2/13/17

6
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Highest score?

I know as of now the policy for the autograder runs, the last run is your final score. Is it possible to take the highes
2/13/17

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Search function return location

When we set a location to the location of the found string in the search function, should we create a new location objec
2/13/17

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How do we handle inserting of large text into one line?

I am failing insert_test_1 as well, and I have a hunch they are inserting giant pieces of text. However, when something
2/13/17

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Print document empty error issue

For some reason, when I open up a file that doesnt exist or has no lines, the editor says there are no lines to display
2/13/17

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failing insert_test_1

I am passing all the tests except this one. I have looked at @879 but still wasn't able to come up with anything
2/13/17

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Instr Quiz 2

Quiz 2 is this week in the CBTF https://cbtf.engr.illinois.edu/ you should sign up soon. The dates for this quiz are fro
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2/13/17

2
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split

for the split function, if a line has index from [0,8], is it guranteed that the cursor location will be within that ran
2/13/17

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How delete works

Does delete work like backspace on your keyboard or does it work like delete? Meaning if I have "HelloWorld" and
2/13/17

7
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Editor_main keeps cursor index when all lines are deleted

What should we do in this case? When the user deletes all lines (making the document empty), the main editor program kee
2/13/17

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Instr (pid=9001)/home/evans/shell$ release

We have released the shell MP !This mp is located in your svn repo at: https://subversion.ews.illinois.edu/svn/sp17-cs24
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2/13/17

6
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Invalid addresses/bad frees

Can someone explain a little more what would make the address invalid? Is it just if it's not pointed to by any of t
2/13/17

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Invalid call

If I first call mini_realloc with requested size equals to 0, then I call mini_free, will that be a invalid call?Since w
2/12/17

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Inserting text clarification

What is difference between "insert to a line that does not exist yet" and "insert past the end of line"
2/12/17

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Display error or function error?

Using the actual editor to add stuff on Mac, has anyone else been getting this? I think it's a display error with my
2/12/17

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is this the right behavior for print_empty_document_test ?

when I try to run the editor with the file name that doesn't exist (./editor empty.txt) it appears like above. A
2/12/17

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Separate strings or not

In the example given on the website when we insert "peanuts" to "mug" at index 1, we get "mpeanuts u
2/12/17

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Append Tests & Print Tests

I am really stressing out now. After yesterday's panic attack and 5 hours more of working on the MP today, I only h
2/12/17

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Document_get_line always fails

Whenever I use Document_get_line or Document_set_line passing loc.line_no I always get an assertion error despite it in
2/12/17

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How to modify the ret value of strdup

for the insert function, i'm using strdup, but since it returns a pointer to a string, we can't modify that stri
2/12/17

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search command

I am kind of lost in the middle. What I tried to do was something like while ( i < doc_size(doc) + 1){ const c
2/12/17

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Changing Default Shell in VM

Has anyone figured out how to change the shell that appears when you log into your VM? I've tried chsh -s /usr/bin/
2/12/17

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if (answer = 42)

if (answer = 42)i am confused how does this line of code evaluated/functioned?
2/12/17

3
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merge oddness

When I backspace from the s position, it merges fine, but the cursor automatically moves to the next character. I don&
2/12/17

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sizeof

If an integer is 4 bytes. int A[8]; what is sizeof(A)? Would it be 32?
2/12/17

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realloc

If we call realloc inside of mini_realloc, and realloc happens to return a newly allocated chunck of memory, then the pr
2/12/17

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mini_calloc

Should each chunk allocated in mini_calloc have its own metadata, or does the entire larger section have one metadata?
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2/12/17

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Is the text-editor supposed to be like this?

when I go the the next line by pressing enter, it goes to the next line without problem, but when try to type somethi
2/12/17

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insert command error

Lets say my document currently has two lines 1 mug 2 salf On my editor_test.c, I tried to add the third line by doing
2/12/17

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Hitting ENTER at end of document

Mentioned in @867. Bringing this up again because I'd like to know what the expected behavior is. As far as I ca
2/12/17

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extra memory usage

I only malloc 20 bytes in my test.c. However, why I run the mini_valgrind the output is that: ==26929== ==26929== Progr
2/12/17

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safe to assume that a chunk of memory's metadata will always be directly "behind" it in memory?

I'm not sure how else to access the metadata for freeing in mini_free.
2/12/17

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Can anyone please explain this piece of code?

typedef int (*comparator)(void*,void*); int greater_than(void* a, void* b){ return a > b; } comparator gt = grea
2/12/17

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Midterm

When is the midterm going to be?
2/12/17

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Handle_display numbering

Little confused about the numbering for handle display. Say I have the following: This is line 1 This is line 2 This is
2/12/17

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sematic of search function

suoopse a file contain 10 lines, our start location is at line 5, than a complete run should be 1. from 5 to 10, if not
2/12/17

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find current location

in search function, after we use strstr() and get the pointer, how do we find the character index of the return pointer?
2/12/17

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Finally, the search wraps around the file. So if we search for bee one more time:

Finally, the search wraps around the file. So if we search for bee one more time: for the search, what function can we
2/12/17

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Question regarding wiki

I had a question regarding the wiki, it says the following code does " This declares a function type comparator that
2/12/17

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Are we supposed to be unable to add new lines ?

So here's what I did. I created a doc with 3 lines 1 mug 2 salt 3 T.V. remote and then deleted line 2 making it
2/12/17

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replacing the string

For the insert command, I know that we have to get the original line by using the Document_get_line command. But i am
2/12/17

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Instr Autograder Lab Mini Valgrind Released!

AG Mini_Valgrind is online! Schedule:"2017-02-12 22:00", "2017-02-13 22:00", "2017-02-14 22:00"
- An instructor thinks this is a good note
2/12/17

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Scroll not working on text editor

I am not sure if it's because I implemented handle_display_command incorrectly (which I think I've done correctl
2/12/17

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Testing With Editor: Search function generates an error after returning the correct value.

While testing the search function in the editor, I noticed I was receiving the following error: editor: vector.c:138: v

▾ Week 2/5 - 2/11

2/11/17

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insert command

So for this one we have to use loc.line.no and loc.idx. I know that we can just use document_insert_line to insert at t
2/11/17

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handle_delete_command

after we call handle_delete_command(delete characters), the "abcdefg" will be "ab fg" or "abfg"
2/11/17

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Anyone passed find_test_multiple_exist_test()?

I have absolutely no clue what this is and i have done everything i can. Since i am passing the rest of the cases, i rea
2/11/17

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what to do when you feel like you've tried everything?

Maybe this is a dumb question, but I'm really at a loss for how to approach this situation, and it's happened to
2/11/17

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Requesting Course Staff to Explain Autograder

I have spent a lot of time working on this MP, and I have done all of the following: Read the docs (both website & .
2/11/17

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What does printing_test1 do?

According to the test description, printing_test1 test print with different windows settings. Is it testing on handle_di
2/11/17

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invalid free case

How to handle invalid free in mini_realloc and mini_free? If the address is not in the list, except for calculating the
2/11/17

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Test by writing white spaces

I passed all test cases but failed the last one, write_white_spaces_test. I'm not even sure what this test case test
2/11/17

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understanding auto grader

So I only passed 8 out of 20 on auto grader but I passed my own test case( has edge case and are very thorough). I also
2/11/17

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failing insert_test_1

I test a lot of inserting, basically every case I can think of, in TUI and everything seems good, but I am still failing
2/11/17

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how do we have to use location?

So the location struct is given to use, and it contains the line_no and the index. On the handle_insert_command, we hav
2/11/17

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contradiction

Docs for merge and the example given for merge still contradict each other. @742
2/11/17

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handle_display_command

So for this function, we are supposed to print out 'max_line' lines of the doc starting from 'start' or
2/11/17

2
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Does the quiz cover fork?

We went over it on the dying minutes of the final lecture of second week, but the post (about quiz1) also says we will o
2/11/17

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editor_main and editor_test

Is the editor_main file provided for us to test our code more easily? For example, if we want to know how it's suppo
2/11/17

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Can anyone clarify insert?

In the document Additionally, keep in mind that for all functions that take in a location or line number, the line numbe
2/11/17

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handle_create_document and Document_create_from_file

The function handle_create_document uses document.h's function Document_create_from_file. Since instructions say th
2/11/17

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memory placement strategy question

https://github.com/angrave/SystemProgramming/wiki/Memory,%20Part%201:%20Heap%20Memory%20Introduction The wikibook tells
2/11/17

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./editor won't fully run

My editor.c functions are all work when I test them with my own test cases in editor_test.c but for some reason when I r
2/11/17

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weird extra spaces in editor test

Is this happening to anyone else? When I run ./editor test.txt, on the end of some lines, there's a few extra spaces
2/11/17

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Hitting ENTER at end of document?

I am experiencing strange behavior. I made a condition that if I hit ENTER at the end of the last line of the document,
2/11/17

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insert/delete taking care of memory

For either of these we need to modify an existing line. Since we worked with vector last mp, we know that there is memor
2/11/17

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Why the random number is the same?

Hello, I noticed that this code snippet on the handout what we did not touch in lecture. I understand this code
2/11/17

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deleting characters

Should we be actually changing each character to "" to remove the space it occupied int he string before, or is
2/11/17

2
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Conflict with delete

@817 and @847 are in conflict regarding whether or not lines should be shifted up after deleting one. Seeing as
2/11/17

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Confusion about location

In the case where location line no is invalid (less than 1 or greater than doc size), should we catch this with an asser
2/11/17

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\n in insert

I'm handling my insert by copying chars over from both the existing line and passed in line to a new buffer. If I
2/11/17

2
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If filename doesn't exist

In this MP, it looks like that if the pathtofile is not a existed file, then the program will just fail? Does this mean
2/11/17

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strcat output as a parameter to Document_set_line doesn't work

I'm implementing merge, and I used strcat to concatenate line_no and line_no+1. When I try printing the output o
2/11/17

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what is a buffer?!

I realize this might be a silly question, but can someone please explain what a buffer is/the significance? the term is
2/11/17

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Is test case graded?

If so, can I use my own pointers_gone_wild MP as part of my test without being considered plagiarizing?
2/11/17

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Intro to C Wikibook question

https://github.com/angrave/SystemProgramming/wiki/C-Programming%2C-Part-1%3A-Introduction One section on this Intro page
2/11/17

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is it possible that other tests will fail because insert does?

I'm very confident in my search command function, but I seem to be failing all three tests. I'm wondering if it&
2/11/17

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print ag

Do the tests labeled print in the AG have to do with handle_display_command?
2/11/17

2
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Instr Beware of strncpy()

I've noticed that this function has been the bane of many students' otherwise correct(ish) code. So let me just
- An instructor thinks this is a good note
2/11/17

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line indexing

just to confirm, even though the lines of the document are 1-indexed, the underlying vector of the document is still 0 i
2/11/17

2
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mutiple_inserts_same_line_test

Could someone give me a hint on what this test is about? I tried testing multiple inserts at the same line on my own and
2/10/17

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simple question about string

So I know that the string can be represented by either char*s or char s[] And I know that the difference between those
2/10/17

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Run GDB with mini-valgrind?

Simple question, but I've tried and couldn't find an answer: How do you run GDB while running mini-valgrind? I&
2/10/17

2
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Delete command

/** * Delete 'num_chars' characters from 'document' at 'loc' onwards * Note: if strlen(line) -
2/10/17

3
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split an empty string

I am not quite sure about the case when we are going to split a empty string, do we need to split a empty string in the
2/10/17

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Assert vs print_usage_error

For functions like: handle_display_command(Document *document, size_t start_line,size_t max_lines) Should we assert(star
2/10/17

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Index vs strlen(currentline)

In handle_search_command, what is your loc.index is GREATER than the string length of your current line? I looked throug
2/10/17

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handle_search_command line clarification

Lets say you have a file with the following line: the [b]ee movie is the best movie ever made. where the square bracke
2/10/17

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handle_delete_command

For insertion, handle_insert_command() can apparently be called on lines that do not exist yet. Can this be called for h
2/10/17

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Confusion regarding find_test_multiple_exist_test

Find multiple lines with a given key after writing them. My understanding is that the test is expecting me to send the
2/10/17

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Document save?

I am confused about this function. It says that the document write itself to a file with the specified name. But when I
2/10/17

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Delete line

I have successfully deleted a line, but the line remains blank. I need to shift the entire document up, I am thinking ab
2/10/17

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cursor pass the end of string

When I use TUI interface, I found that I could move the cursor pass the end of string. And when I delete or insert chara
2/10/17

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Overflow in mini_calloc

In mini_calloc, do we need to check that num_elements * element_size doesn't overflow?
- An instructor thinks this is a good question
2/10/17

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Text Editor Insert Tests?

So, on the last auto grader run, I failed "inserting_test", but somehow passed the "more rigorous" "
2/10/17

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Pointer Arithmetic

On a lecture handout, int *x = & 0x12340; On a 32 bit machine, what is the value of (x + 1)? The professor st
2/9/17

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empty_document_test

After 2.9 AG, I have the following question: I set if (Document_size(document)==0) print_document_empty_error(); in my
2/9/17

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checks

do we have to check for boundaries like if line_no = 0 and line_no > document_size or make asserts such as that docum
2/9/17

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mini_free() in mini_valgrind.c

To my understanding, free function in mini_valgrind.c has the time complexity O(n) right? As we have to iterate through
2/9/17

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Clarification on handle_display_command

In the documentation, it says when calling hand_display_command(document, 1, 5) on mug salt T.V. remote it will print o
2/9/17

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weird leaks

I get these weird leaks reported when I run mini-valgrind: ==4723== LEAK REPORT:==4723== Leak origin: __strdup (/lib/
2/9/17

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newline in the text editor

Are we to assume that every line in the test editor needs to end with \n?
2/9/17

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Wikibook Question Answers

Hi, are there any answers to the questions at the end of the wikibook review section? If not, specifically I would like
2/9/17

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Nvvm

Nvm
2/9/17

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Purpose of waitpid?

if the system takes care of zombies for us by assigning child processes with a 1 after the parent process finishes and t
2/9/17

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How to find the associated meta_data in realloc?

in the mini_realloc, how do we find the associated meta_data of the given pointer? Can we use the filename and instructi
2/9/17

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Confusion about forking

I'm a bit behind, so I am just catching up. I ran into some confusion with using waitpid and fork. So basically if I
2/9/17

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(Resolved)

I think there may be a bug with this lab involving free(). For some reason an extra pointer is being passed to mini_free
2/9/17

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Instr Vector Assignment Feedback

Here is the feedback we got from the Vector assignment! Thank you to all who submitted your feedback. For the next assig
- An instructor thinks this is a good note
2/9/17

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Deleting line

When we handle a "delete line" command in editor.c, should the subsequent lines shift up or should a blank line
2/9/17

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undefined behaviors

When the header file says this: * If the given pointer is NULL, you should treat this like a call to
2/9/17

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Split Edge Case

If you attempt to split a line at an index past the length of the line, does it split into itself and an empty line, or
2/9/17

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Lab attendance

If we need to miss our lab section and attend section ADH instead, do we still need to get permission from our original
2/9/17

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head ptr

Since the header notes for mini_malloc say we insert the meta_data into the head of the list, this would mean that head
2/9/17

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Discussion Attendance

Are we allowed to miss two discussion sections or three?
2/9/17

2
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how do we change a discussion section?

Hi! Now the deadline for changing section has over. What if I wanna change the section?
2/9/17

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Instr Mini Valgrind leaked!

The Mini Valgrind lab has been released. This lab is located in your SVN repo at https://subversion.ews.illinois.edu/svn
- An instructor thinks this is a good note
2/9/17

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references to environment variables

Now that the lab has been submitted, i hope it is fair to ask this question. can someone share their ideas as to how to
2/9/17

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Instr Autograder MP Text_editor Released!

AG Text_editor is out! Schedule: "2017-02-09 22:00", "2017-02-10 22:00", "2017-02-11 22:00", &#
- An instructor thinks this is a good note
2/8/17

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test

so originally, my SHLVL=1, after I run ./env SHLVL=2 ls then i run ./env, my SHLVL is still 1. is that what suppose to
2/8/17

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Error: using the provided strsplit()

My code works fine, but when I call strsplit() (the provided one under resources) on more than one variable from the var
2/8/17

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fork example from lecture

I tried the simple forking example that was shown in the lecture but it seems to show weird behavior. Why is the
2/8/17

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Without arguments env segfaults after it prints all the env variables

Program received signal SIGSEGV, Segmentation fault. 0x00007ffff7a5ccc0 in _IO_vfprintf_internal (s=0x7ffff7dd2620 <_
2/8/17

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Is a var-list which has a comma as its last character considered invalid

I am trying to decide how to handle an input which has a valid var-list but ends in a comma. Something like "./env U
2/8/17

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Reference

For env.c , I heard there was a reference last semester, do we need to follow that reference or follow the actual enviro
2/8/17

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What's the point of 'close'?

I know that the close command closes the integer file descriptors associated with the streams stdin, stdout, and stderr
2/8/17

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env confusion

./env PATH=%HOME/bin:%PATH, .....on the right of "=", there are two environmant variables, HOME AND PATH. does t
2/8/17

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sleep question

I'm running my tests with sleep 2, and when I ran in gdb, it looked like it did in fact measure the time it took to
2/8/17

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Exec failed

It worked fine when I ran ./env PATH=%HOME/bin:%PATH,IDIR=/%HOME/include,LIBDIR=/%HOME/lib printenv But when I ran ./
2/8/17

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Resetting Environment Variables

After we set the environment variables with the input parameters and then fork and run the child under those new conditi
2/8/17

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Valgring on Utilities Unleashed

Do you check for memory leaks in any of the tests? I'm leaking a little memory but who died because of leaking a li
2/8/17

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When exec fails do you still want to print the time it took your program to run?

-
2/8/17

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serching text not found

Since the search command will wrap around the file, what should we do when the test is not found? (to avoid an infinite
2/8/17

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make unfound

./env PATH=%HOME/bin:%PATH,IDIR=/%HOME/include,LIBDIR=/%HOME/lib make -j4 I tried to run the given command without ./ t
2/8/17

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delete handle input question

If y'all give us a loc with index 0 to delete from, should we interpret that as actually deleting the whole line? Or
2/8/17

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Different output when running on debug build

When I run ./env TZ=MST7MDT date I got something like Web Feb 8 23:04:03 2017 which I believe is wrong. But when I
2/8/17

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Clarification on env test cases

So I'm still a bit confused about the reference env test. Let's say if we have ./env %PATH=Hello ls I know this
2/8/17

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handle search edge case

Should we consider the case where a query string overlaps lines, i.e. starts on one line and ends on another?
- An instructor thinks this is a good question
2/8/17

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expected output for env_test_ref and env_test_ref_empty

I read some posts about both cases like @728. But still I have a confusion. for env_test_ref_empty So if we put like
2/8/17

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segfault strlen()

I'm trying to use strlen() on the string returned by getenv(), but gdb gives me this message: [Switching to process
2/8/17

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Error Catching setenv()

Hi I'm trying to catch when setenv fails by seeing if the return value is -1 but I am segfaulting even before this h
2/8/17

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failing time_test_exec

I think when exec fails the only thing we need to do is print_exec_failure and exit(1) in parent process, and my output
2/8/17

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Testing?

This is a pretty obvious question, but when i do ./env TZ=MST7MDT date I know that TZ should be changing. But where ex
2/8/17

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Exiting after incorrect usage

If we run into any errors like a failure to execute the given program, failure to set a environment variable, or a failu
2/8/17

2
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ref question

From the webpage, it said that "env updates the environment variables sequentially. For example, ./env PATH=%HOME,ID
2/8/17

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Invalid variable exception.

when the input is %fdadsfadsfadfadfdaf=abc Since the left hand side is not a legal env variable, we should make it to b
2/8/17

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Error handling

If the code entered was: ./env TZ=MST7MDT,=10 date should that set TZ=MST7MDT then call print_env_usage(); or just call
2/8/17

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Purpose of argument

What's does the argument 2 in code "time sleep 2"do? why do we need to handle the "2" if time is jus
2/8/17

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%notations

The notes for utilities unleashed asks us to make a function to get all the % notation. In an example string such as PAT
2/8/17

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0 allocs, 0 frees

I got the right output, but when I was trying to use valgrind to check memory leak, it says" 0 allocs, 0 frees",
2/8/17

2
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bash command not found for time

When running ./time if we try it with a command that would normally result in "bash command not found" what shou
2/8/17

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is this what im supposed to get when I run env with no argument?

Is this what I am supposed to get when I run with no argument>
2/8/17

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When do we use exec() in env if we cannot use built-in env?

I am little bit confused about that. If we cannot use built-in env, we are supposed to print, change environment by usin
2/7/17

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Can we put char** envp as parameter of main?

Is it allowed to use that syntax?
2/7/17

3
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Finding text

In the document for text editor, it states that the TUI automatically increments the character index by one so that the
2/7/17

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env clarification

when I type the following in the command line ./env PATH=/%HOME/something_here command_here And HOME is /home/my_netID
2/7/17

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print env

I use a loop to print all the environment variables in enc.v when there is no argument as required. However, when I comp
2/7/17

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lecture 5 question

This is the code using execvp that the professor fixed in the lecture. I dont quite get why argv+1 didn't wo
2/7/17

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Second-to-last autograder tomorrow

For utilities_unleashed, is the second-to-last autograder going to be run at 12 PM as was announced in @610, or at 2
2/7/17

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Time: clarification

In this situation, should we call print_time_usage() or print_exec_failed() ?
2/7/17

2
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time_test_usage?

What exactly is this testing? I am able to pass the other time tests but not this one. I follow the fork-exec-wait patte
2/7/17

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what exactly is idx?

editor.h defines it as: /** *
2/7/17

3
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When using execv for testing time

I try to pass char *const args[] = { "ls -l", argv[2], 0}; execv("/bin/ls", args); Why is the first pa
2/7/17

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Text Editor Line Overflow TUI Weirdness

I've noticed that in the TUI for the text editor, if you have a line that wraps around (i.e. is longer than your ter
2/7/17

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Text Editor Clarifications

1) At least three functions claim to be one liner so far. Are they a bit misleading? For instance, for the get_filename(
2/7/17

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Time Weirdness

For some reason my program only works sometimes. What's going on?
2/7/17

3
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Exec

I know that you are supposed to call the print_exec_failed() if the exec fails to exec, but assuming the fork doesn'
2/7/17

2
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Any mp/lab second chances in the end of the semester?

You can tell that this is a desperate post.... I've heard that last semester they had two reruns for both the mps an
2/7/17

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env.c

in format.h it specifies that we should use print_environment_change_failed if the function setenv( ) fails. However wou
2/7/17

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Quick question for compile error

Hi, I'm trying to test my time function, but every time I "make", it keeps giving me error below. I do not h
2/7/17

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Understanding getenv()

PATH=%HOME/bin:%PATH,IDIR=/%HOME/include I don't seem to understand how this works with getenv, so the srcvar is HO
2/7/17

2
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invalid variable name

It says The names of the variables <destvar> and <srcvar> will contain only letters, numbers, or underscore
2/7/17

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Can we use the example of stringsplit code?

Can we just use the one provided or we have to write our own stringsplit function?
2/7/17

2
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Lab Slides

The lab slides online seem to only have the headers and not the content we went over in lab, would it be possible to upl
2/7/17

2
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handle_merge_line

In "editor.h" it requires to merge 'line_no'th line in document with its following line. However, the MP
2/7/17

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Testing using editor_test.c

How do I create a location struct in editor_test.c? Otherwise it's impossible to test functions that take a location
2/7/17

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No filename

What do we do in our code if the user doesn't give a file name? i.e. they just use: ./editor Is this undefined behav
- An instructor thinks this is a good question
2/7/17

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Editor.h updated - no get_filename?

After the doc were changed and I ran svn up to get the changes, editor.h seemed to have been changed. Original: char* g
- An instructor thinks this is a good question
2/7/17

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env workflow

I finished my env, but am not sure if I'm doing it right. I use the child to change the environment variables and th
2/7/17

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time

I don't understand why I'm getting 0.000000 seconds whenever I try running time. execl("/bin/sleep",
2/7/17

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Instr Text Editor docs updated

Hello! There has been some clarifications made for Text editor MP on the boundaries of location that are allowed in &#
- An instructor thinks this is a good note
2/7/17

2
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wikibook update

can the wikibook readings be updated on the calendar please?
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2/7/17

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as the dealline has past

what is test_accesors?
2/7/17

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argc > 2?

will we ever have to worry about this?
2/6/17

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sshfs question

I was trying to set up sshfs on my own Mac. At the step of "Mounting the Remote FIlesystem", sudo sshfs NETID
2/6/17

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Tests

I am passing env_test, one, two but failing exec, ref, usage, and ref_empty. I guess for ref_emtpy you are testing some
2/6/17

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using exec

for time, i still do not understand which exec function should be used and how to use it. if someone could clarify this
2/6/17

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call multiple strtok

So if I call multiple strtok with different strings and different delim will it be messed up if I do strtok(NULL,",&
2/6/17

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condition for print_exec_failed?

The format.h says print_exec_failed gets called whenever env or time fails to execute. How do we have to set a condit
2/6/17

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print_line function in Text Editor indexing?

So, in the format.h file, it says the following for the "print_line" function: /** * Prints out one line from
2/6/17

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Mem leaks if assert was invoked

How to deal with memory leaks if assert was invoked before we actually destroyed the document?
2/6/17

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Valgrind errors

Hi there. So I have memory leaks at the while statement when I run valgrind. I am not sure why exactly but I am apparent
2/6/17

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Question about background running

One the wikibook page, it says we have to set the parents not to wait for their parents if we want to start a backgroun
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time_test_exec

I failed the time_test_exec test case, which is when exec is supposed to fail. I understand that nothing under the exec(
2/6/17

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vector_insert- position an indice or the number of the element?

Is position supposed to be an indice from [0, size) or the number of the element?
2/6/17

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destructor double free?

Valgrind tells me I have an double free here, but there is definitely still an int inserted at the end of this pointer.
2/6/17

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document test segfault

Hi, I have a really strange problem. I wrote a test case where I make a document from a file then write to another file.
2/6/17

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handle_insert_line() Behavior Regarding Inserting Into A Non-Existent Line

If you insert at a line number that does not exist yet, how do you to take into account the location's idx field (if
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2/6/17

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Vector Resize

If the requested size is > the current capacity, should we set the new capacity to the requested size, or use vector_
2/6/17

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why execlp(set...) fialed?

When I have this in my code, exec failed execlp("set","set",(char*)NULL); but when I use
2/6/17

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Nothing printed to console

So I have the following line: document *new_doc=document_create_from_file("whyisnowork.txt");for(size_t i=1;i&l
2/6/17

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AG run after deadline

Will the autograder still be running after the deadline? I want to still be able to debug my code and continue testing j
2/6/17

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Should vector_set(position) reserve space if position is greater than vector's capacity?

In the header file there is no specification of how vector_set should handle vector_set(position) inputs where position
2/6/17

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env testcase

How could we test that the env variable is set correctly in the child process? Thanks.
2/6/17

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invalid time interval

sleep: invalid time interval ‘ \n@’ Try 'sleep --help' for more information. sleep 2 took 0.000000 seconds
2/6/17

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Adding elements to document vector

So since the struct document has a vector which is initialized with the string constructors in the document constructor
2/6/17

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Call reserve or resize

In functions like vector insert, do we call reserve or resize? I believe resize would allocate new memory that I don'
2/6/17

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default ctor

seems like the leak is because of the default ctor I call in resize(), but where/what function I need to free the thing
2/6/17

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Document Test

If I create a document from a text file, and then create a new file from the document, should both(new and old files) sa
2/6/17

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Is there a command to see when a specific file was commited last?

I googled it and it said svn log shows a list of commits(without file names only times) but what if I want to see like a
2/6/17

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using string constructors

I'm a little confused how we use the string constructors given at the beginning of document.c on our vector. Do we i
2/6/17

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memory error

Program received signal SIGSEGV, Segmentation fault.0x00007ffff7a91982 in __GI___libc_free (mem=0x7fffffffe440) at mallo
2/6/17

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Are we reallocating the entire vector or just the array?

When the size exceeds the capacity, do we only need to reallocate the array or can we reallocate the entire vector?
2/6/17

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Looking at past commit

Hi, is there anyway to look at or revert back to a previous commit on svn? Just wanted to make sure before I do it.
2/6/17

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vector _insert past capacity?

A course staff told me that clients need to be able to insert anywhere in the vector, even outside capacity (just like i
2/6/17

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testing push_back. Will this pass?

Here is how my test case for push_back looks like. I appended "j" 13 times and tried to print it by using the
2/6/17

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Default values in resize get wack

In my resize, I use the default constructor to assign the default values to the empty spaces when passed size is > cu
2/6/17

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vector_clear

Should I call vector_destroy in vector_clear()? Or should I only call vector_resize(this, 0)?
2/6/17

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insert empty string

So I used vector_insert(this->vector,i,""); I'm not sure it it's right, or I have to malloc one b
2/6/17

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free when no memory allocated

When I try to use this->destructor(this->array[0]), I get a memory error saying I freed memory that wasn't mal
2/6/17

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vector_begin

I was having problems with vector front, so I ran tests with vector_begin and it returns the address of the copy_constru
2/6/17

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Vector_insert and size

Will it matter when we update size with regards to inserting an element? By this I mean, should we increase size by 1 be
2/6/17

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vector_set, vector_push_back

For vector_set, vector_push_back, I use copy_constructor to put elements into vector->array. Then, should I free "
2/6/17

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vector_pop_back help

I've been testing my vector_pop_back function which uses the vector's destructor method to get rid of the last e
2/6/17

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Valgrind Error

I'm getting this error when I run valgrind, and I'm not sure what the top part means. The line under "Thre
2/6/17

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Fail resize/reserve test

Does it matter if I change the INITIAL_CAPACTIY? Is that possible that I fail the auto grader because I change this line
2/6/17

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push_back 100 times -> gets weird char

This is how my test case looks like. I tried to push back "1" 100 times on my char vector, and printed the vec
2/6/17

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Confusion with Empty Files and Empty Documents

If we try to pass in a non-existent file to document_create_from_file() do we return an empty document or NULL. The docs
2/6/17

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env_test_ref_empty clearification

Can someone please confirm what we are supposed to do for env_test_ref_empty? I assume this tests situations such as ./
2/6/17

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vector_resize < this->size

If the size of a vector is 10, and it gets resized to 7 with vector_resize(), are we supposed to call the destructor pas
2/6/17

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Initial Capacity in Vector

Most people probably won't make this mistake, but I thought I'd post it anyhow. The vector's initial capac
2/6/17

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Accessing front

I saw an earlier post mentioning the correct syntax to access array elements. My vector_front returns this->array[0]
2/6/17

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How would you pass in constructors as parameters to functions?

this vector_create(&string_copy_constructor,&string_destructor,&string_default_constructor); or vector_cre
2/6/17

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failing resize_to_smaller_size

I wrote my test case and my resize() works as expected. Is it possible that something else causes this test to fail? Do
2/6/17

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env case with references

./env PATH=%HOME/bin:%PATH,IDIR=/%HOME/include,LIBDIR=/%HOME/lib make -j4 I have a few questions about this example usa
2/6/17

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Second to last autograder time change request

Could the second to last autograder time be changed from 12PM to 6PM always? I think it's not that helpful to have t
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2/6/17

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Destructor

In the destructors given in the callback, it only frees the argument. So, if I wanted to delete something in the array I
2/6/17

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Default_constructor in resize

I'm a bit confused about how to handle resize with regard to default constructor. What I'm doing now is loopin
2/6/17

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Passed vector test cases. Question regarding final autograde run.

If I try to pass document test cases which are the remaining 5 point and the AG comes across a segfault while testing my
2/6/17

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Instr Uber Tech Talk at UIUC

Hi Everyone, My friend Henry Lin who is a recent alumn of the 5 year MS/BS in CS program and long time TA for CS 173, 2
- An instructor thinks this is a good note
2/6/17

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Instr Rerun Autograder Lab Utilities_Unleashed!

We have rerun AG for Lab Utilities_Unleashed at 2:00am this morning. Most of you won't be affected by the rerun. But
- An instructor thinks this is a good note
2/6/17

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failing the doc tests

Is using fopen with "w" sufficient for the r/w permissions of writing docs? Others have commented that it worked
2/6/17

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Instr Quiz 1

Quiz 1 is this week in the CBTF https://cbtf.engr.illinois.edu/ you should sign up soon. The dates for this quiz are fro
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2/6/17

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How to instantiate the constructors and destructors in vector_create()

Hi,I am a bit confused about how exactly should I instantiate the pointers to the constructors and destructor functions
2/6/17

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Wrong output

When I run the following in vector test: vector * our_vector=vector_create(char_copy_constructor,char_destructor,char_
2/6/17

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Autograder Feedback?

Are we supposed to not get Autograder feedback? This is the same output that I got before I committed my code. If this
2/6/17

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Insert

Just wanted to make sure so position could not be 0 since that would mean we are trying to place the element before the
2/6/17

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realloc() for reserve

My realloc() works once, and then segfaults. I don't understand what's going on. this->array = reall
2/6/17

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No op for resize

How can resizing vector using vector_resize not use malloc when size < n < capacity? Aren't we supposed to use
2/6/17

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Insert_One

For some reason my insert_one and insert_many tests fail. Although when I test it on my own, they seem to pass. Any reas
2/6/17

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Accessing elements of array incorrectly?

I was wondering how we were supposed to be accessing the elements of the array because I am having some difficulties dra
2/6/17

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is size something that has to be managed separately? (just for clarification)

I was wondering if the size of the vector is just a separate variable that has to be managed separately regardless wha
2/6/17

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Memory leaks document.c

Are we responsible for freeing the memory allocated by document_create() inside document.c? In which function would that
2/6/17

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env: clarifications

Some of these questions like this have been asked several times but they've either yielded conflicting information o
2/6/17

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resize

Resizes the container so that it contains 'n' elements. * * If 'n' is smaller than the current contain
2/6/17

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Confusion on Reading from file

I am confused about the newline at the end of each line. For example, if there is an input.txt HelloWorld Then after cal
2/5/17

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About terminal newline : File with no newline character has zero line?

“A sequence of zero or more non-<newline> characters plus a terminating <newline> character” Therefore ther
2/5/17

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Is it possible to get a 0 on AG because of a vector_create fail?

I believe there may be something wrong with vector_create from these error messages. ==9645== Invalid write of size 8==
2/5/17

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failing insert_many

I am failing insert_many and I thought I fixed it but guess not. I have tried some tests but wasn't able to find any
2/5/17

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Confusion on document_create_file?

I am kind of confused on what the purpose of document_create_file is? Is it to create a new document from a given file?
2/5/17

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How to Pass the Autograder on No-Op Tests

I'm not sure how to pass the tests in which nothing is supposed to happen. For example, my resize does nothing if t
2/5/17

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AG error?

I passed every test in my document_test.c but I failed almost every AG test for document. I set the flag to read and wri
2/5/17

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How can I use Valgrind to check memory leak of program with exec?

I want to check the memory leak to the child process, but it was replaced by other process. When I use Valgrind, it appe
2/5/17

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Constructor for Document

When we initialize our document in <tt> document *document_create();</tt> I assume we have to initialize our
2/5/17

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Adding characters beyongd line size

If we try to add a line beyond the total number of lines, the text editor should insert empty lines to fill in the gap.
2/5/17

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Can the vector have gaps?

Is it possible for the vectors to have gaps? for example the size could be 3, but the data would be at indices 0, 3, and
2/5/17

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Text editor example

Instruction says: Now using the same things_on_my_table.txt file If a user were to call handle_insert_command() with
2/5/17

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Entering data into doc

vector_insert(doc->vector, 0, s1); Doesn't work for me when I want to enter char * s1 into doc's vector, the
2/5/17

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Decreasing capacity

Are we not allowed to decrease vector's capacity when its size is smaller than or equal to half of its capacity? Is
2/5/17

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Assert

In one of my function, specifically insert, I know we should do an assert to make sure the position is actually within o
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Illegal Instruction / no such file or directory

Running vector_test and getting an "Illegal Instruction" error Running it through gdb gives this output I'
2/5/17

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Quiz1

What is our quiz going to be on?
2/5/17

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document_check_memory

I don't have memory error in vector, however I am having this invalid read error: ==6869== Invalid read of size 8 ==
2/5/17

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size vs capacity question

Since size is the number of elements that exists and capacity is how much it can hold. Is it possible to have a vector
2/5/17

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document write_to_file

is there a flag we should use to make sure the data is overwritten if the file already exists?
2/5/17

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Getting memory leak at document_create()?!

I am completely despairing. I have read over my code multiple time but I can't seem to understand why I am leaking m
2/5/17

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forward declaration of 'struct vector'

When trying to use vector in document.c document_write_to_file, I get the following errors:in vector.h: forward declara
2/5/17

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anyone use realloc rather than malloc for resize() and pass the testcase?

for the resize function, for the reallocation case, is it possible to use realloc rather than malloc. altough realloc wi
2/5/17

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can we fail all the document ag functions if we don't set permissions to rw for others

I'm failing every autograder function, despite trying most of the things the autograder lists and succeeding in my o
2/5/17

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Creating Environment Variable

If we call ./env telling to to edit a environment variable that does not exist do we just let "setenv()" fail an
2/5/17

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Instr open("Text Editor", O_CREAT);

We have released the text_editor MP ! This mp is located in your svn repo at: https://subversion.ews.illinois.edu/svn/sp
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2/5/17

5
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Should destroy free vector itself?

I allocate memory in vector_create() so I wonder if I should free it in destroy? I mean free vector itself and all the
2/5/17

2
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Resize: N>capacity instruction clarification

To be 100% sure: if n>capacity, then we just change capacity, and size DOES NOT get changed right?
2/5/17

6
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vector_test.c how can I print out my vector to check for output?

I tried to compile my vector_test and try to print out the vector to check for output. But I keep getting this: vector_t
2/5/17

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meaning of this error?

Trying to compile your code... Successfully compiled your code.. ==22339== Memcheck, a memory error detector ==22339=
2/5/17

0
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Lab env get the referencing none-existing environment variables

Hello, I am wonder if we do something like ./env PATH=%HELLO sleep 2 (assume that HELLO is not defined as a envi
2/5/17

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Instr Kickoff: Go Patriots!

vote 4 your team! [o] Patriots [o] Falcons [o] Yay sportsball!!!
2/5/17

6
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Instr Autograder Lab Utilities_Unleashed Unleashed!

Utilities_Unleashed AG is online! Schedule: "2017-02-05 22:00", "2017-02-06 02:00",----rerun AG "
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2/5/17

8
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Clarification of "position"

Suppose a parameter has position = 4 when calling vector_get. Are we returning position 4 (arr[4] or the 4th element (a
2/5/17

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vector_destroy function. How do we know the user provided destructor is robust enough or not

If we are able to free up all the individual vector elements by our self and set them to null what is the user provided
2/5/17

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Error in Document.c given function?

When I try to make, I get the following error: document.c:118:1: error: unknown type name 'Void'; did you mean &
2/5/17

4
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vector_pop test

I'm failing vector_pop but passing vector_push_pop. I've tested pretty extensively and had no problems with this
2/5/17

0
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Using getline() for document_create_from_file()

I was using getline() for document_create_from_file() and was running into a bunch of problems when trying to write to t
2/5/17

3
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vector_get and vector_at

According to vector.h, vector_at couldn't return a pointer when n is out of size range. So my understanding is vecto
2/5/17

2
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When/How to use default_constructor

I'm having trouble figuring out when exactly to use the provided default_constructor. I understand why we need it, a
2/5/17

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for vector_create do we have to make a check for NULL parameters for the function?

Should we not initialize copy_constructor, destructor and default_constructor or just set it to null
2/5/17

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Lab env invalid input

Hello, I am wondering that if we should take care of the case of incorrect input argument. Cases like NAME=ME,P
2/5/17

4
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vector_insert

Do we have to handle the situation when (position >= size)? Or the the position should be assert to be less than size
2/5/17

5
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New Min Capacity

I don't understand what is the min capacity we should set it to after we realize it needs a new capacity. Isn't
2/5/17

4
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Valgrind output from autograder confusion

After the autograder ran last night, I got this error message in my grade report saying that "Line 0 was not the sam
2/5/17

4
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What are "constructor_type" or "destructor_type" ?

I understand how the different constructors are used to keep the vectors' implementation independent of the data typ
2/5/17

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Can we use the identical codes from the previous Lab.

For example, I used some fuctions from read_wrap.c in lab1.
2/5/17

3
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Env bad inputs

1) What should we do if instead of ./env TZ=MST7MDT,FFS=FF date the user entered ./env TZ=MST7MDT, FFS=FF date // space
2/5/17

4
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Resize & memory issue

My vector.c passed all my own test cases. However, it still failed resize_to_initial_capacity and resize_to_smaller_size
2/5/17

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Failing resize_to_same_size, but I shouldn't

I'm currently failing the resize_to_same_size test, but my function explicitly returns whenever a size that's sa
2/5/17

3
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Document Write To File Clarification

In the docs is says: For each line in 'document' write it to the file located at 'path_to_file'with the
2/5/17

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Aborting at reserve, just to check my understanding of the function.

In my understanding, when n is greater than current capacity, we realloc the vector's size using get_new_capacity. I
2/5/17

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Should vector_clear resize?

I'm not quite sure what the documentation for vector_clear is getting at. It says A reallocation is not guaranteed
2/5/17

0
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Failing append_get and append_few

I'm a bit confused as to what I should look for based on the results of my most recent autograde. I seem to be faili
2/5/17

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General free() question

This is in regards to reallocating new memory and copying over values of a void ** array. // void **array already exist

▾ Week 1/29 - 2/4

2/4/17

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Env Clarification

I was wondering which of the exec() family of functions we are allowed to use. For example, are we allowed to use execve
2/4/17

2
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setting the initial capacity

I understand that when creating a vector we need to allocate memory to the array of size INITIAL_CAPACITY * sizeof(void
2/4/17

5
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Document read from file gets

If we are using gets to read text out of the file at the file path, are we expected to use a sizable buffer to fit a rea
2/4/17

5
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Document Cases

I've written tests to create documents from file, insert lines, and write to file, and they all seem to work fine lo
2/4/17

2
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How to keep array contiguous with provided constructors?

My understanding is that all operations adding to and removing elements (or space) from the vector should be done with t
2/4/17

3
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syntax question

would that be the correct syntax to remove an element from the array? I am getting a segmentation fault, even though thi
2/4/17

2
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Question about vector_at

Hi everyone, So sorry to ask such a stupid question, but I am confused about vector_at. The vector_at asks us to return
2/4/17

5
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env argument edge case

The assignment instruction says: When run with arguments, it will be given at least two, and will be called like so: ./
2/4/17

2
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Returning NULL

For functions such as vector_get, that take in a vector and a position and return NULL, what's the point of this fun
2/4/17

2
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push_back implementation

/** * Adds a new 'element' at the end of the vector, after its current last * element. * This effectively inc
2/4/17

3
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Undefined Reference: Can't Figure it Out

When I try compiling vector, I get the following weird error: $ make vector clang vector.c -o vector /usr/bin/../
2/4/17

3
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NULL parameter in vector_create

I'm using destructor in destroy() and copy constructor in set() and push() and I'm thinking what should I do, if
2/4/17

2
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typedef callbacks.h

I'm having trouble understanding the typedef statements in callbacks.h. Based on the other examples of typedefs with
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2/4/17

4
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some questions regarding the vector mp

I am getting a vague understanding of how this MP works, but really want to grasp them perfectly to finish the MP witho
2/4/17

2
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Document_insert_line clarification

Just to be sure. When the docs say to "insert a copy of str into the line_number-th line of the document". We ar
2/4/17

2
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vector_create data types

how does vector_create know the type of the pointers in void**array? Isn't this necessary to know when allocating sp
2/4/17

2
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Using temp variables

void **temp = this->array[0]; Would temp correctly point to the first element (pointer) of the array? Would I also be
2/4/17

6
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What to do with bad inputs

When the user provides bad inputs (e.g. setting array at position 10 when the size of our array is only 5, etc.), do we
2/4/17

2
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Set when position > size

Do we need to include the case where position > size for vector_set and vector_insert? Or just assert(position > 0
2/4/17

2
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Setting permissions in document_write_to_file

I am unsure about setting permissions in document_write_to_file. I am currently using fopen(path_to_file, "w+&#
2/4/17

3
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line_number in document_line_insert

Does line_number in document_line_insert starts from 0? or 1?
2/4/17

2
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env malformed input

If we get malformed input to env, like the following: ./env PATH=/bin,,,asd,asf, ls do we call print usage ("when
2/4/17

2
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get_new_capacity

I am not fully sure when to use the get_new_capacity function. Do we have to use it for the reserve function that requi
2/4/17

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Shallow Vector Clarification

I'm a bit confused with how we deal with the shallow copies of vectors (i.e. when we say vector_create(NULL, NULL, N
2/4/17

1
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Append_1mil

I pass the append_few_get but fail both the 100 and 1million and ideas?
2/4/17

4
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env confusion

I just don't understand why do I have to use fork()? Why can't I just use a loop to set all the env variables, a
2/4/17

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document

When I try to compile document.c I get the following error: document.c:60:17: error: use of undeclared identifier 'S
2/4/17

3
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vector_resize

If my vector size = 2 (holding two random numbers, say 5 and 6), my capacity is 10. I want to call vector_resize to 13.
2/4/17

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/bin/ directory

The lab instruction page gives the following example of the usage of time: ./time sleep 2 But shouldn't it be ./time
2/4/17

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Should the excess spots be zeroed?

["Hello" , "World" , NULL, NULL, NULL] Would the above vector be valid or do the NULL spots need to con
2/3/17

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Little discrepancy in vector.h and vector.c file

Hi. It seems that the vector_set(), vector_at(), vector_get() function in the vector.h are declaring an input named '
2/3/17

1
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Insert NULL

If I want to insert NULL, should I set the element to NULL or the default constructor?
2/3/17

6
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I just want to test this....

In my vector_test.c file, I'm trying to initialize a vector as one would when trying to debug his vector class. I do
2/3/17

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Clear memory if assert fails?

Say someone puts in bad input, and thus the assert test fails. Do we need to free the memory that was allocated by the v
2/3/17

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pop_back

the pop_back is supposed to remove the last element and destroy the removed element What is exactly the difference be
2/3/17

2
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document_write_to_file newline confusion

The document for document_write_to_file says that * For each line in 'document' write it to the file located at
2/3/17

2
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hash_function

In callback.c lots of hash functions are provided. What are they used for?
2/3/17

6
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Position

Sorry for making this post. I've been reading a few piazza post about this and getting confused. If we want to SET
2/3/17

2
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Vector callbacks

I have never dealt with callback functions so I just wanted to get some questions cleared. So on vector_create, my under
2/3/17

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Vector-insert()

If I have a vector whose size is 5 and capacity is 10, then I call insert(this, 20, element), should I reallocate the sp
2/3/17

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Will the position always be decremented before sending it to the functions?

In document.c, the position is decremented before sending it to vector_get(), so should we expect such behavior while im
2/3/17

1
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vector insert and push

1) Can we insert an element in an empty vector (size = 0), so that it behaves like a push? 2) Can we insert NULL in a ve
2/3/17

2
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Vector_test implementation and grading

How are we implementing test cases for this MP? Should we use assert statements, or return something like in Lab2, or so
2/3/17

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Capacity

In the beginning, we set capacity = INITIAL_CAPACITY = 10. As we are resizing and changing capacity, capacity can not
2/3/17

2
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vector_create

Is there a difference between these two instructions: 1. malloc a certain size and use default_constructor to initialize
2/3/17

4
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Is this line wrong?

void **vector_end(vector *this) { return this->array + this->size; } Shouldn't it be void **vector_end(v
2/3/17

2
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undefined behavior

What does this line mean when I access a element on an empty container. "Calling this function on an empty containe
2/3/17

3
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grade report is not in my svn

This morning I checked my vector grade report, and now logging back into subversion, both it and my results.json are sim
2/3/17

5
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vector weird memory error

I am trying to write test case using vector contains int type. When I use the int_copy_constructor to create element and
2/3/17

3
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Instr Autograder Question Policy

Dear CS 241 Students, If you have a question about your personal autograde results after the final autograde, then feel
- An instructor thinks this is a good note
2/3/17

2
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Instr Gradebook is up!

Dear CS 241 Students, We have the gradebook up and updated: https://chara.cs.illinois.edu/gb You can sign in with you
- An instructor thinks this is a good note
2/3/17

4
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vector position

The documentation states, vector_get returns the element at position 'n'. Is this position 'n' 0-indexed
2/3/17

3
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user input in vector_create()

Do we assume that user either does not provide any of their own call back function or provide all of their own call back
2/3/17

2
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Path to file

For document write to file, we're given a char* as our path, but write, fprintf, etc, take either a file* or an int
2/3/17

2
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Argument(s) for vector_test

What should the arguments for vector_test be? For example, one test case calls "./vector_test 18". What does thi
2/3/17

3
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Element confusion

I'm a little confused about the elements that the array points to - specifically where they sit in memory. So let
2/2/17

1
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Documents not terminated by new line.

I am still a bit confused after reading this part from the assignment: Recall that POSIX defines a line as “A sequence
2/2/17

2
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Vector Reserve no-op?

So, I was wondering... If in the specification for "vector_reserve" it says that no action is taken if the reque
2/2/17

4
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get_new_capacity in vector_create

I don't get why there is get_new_capacity inside the vector_create. Shouldn't vector initialized with capacity =
2/2/17

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Tip For Vim Users: Viewing Man Pages

If you are using Vim and you want to view the man page for a certain function, you can place your cursor over the functi
- An instructor thinks this is a good note
2/2/17

1
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vector_at assert

/** * Returns a reference to the element at position 'n' in the vector. * * The function automatically checks
2/2/17

2
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reversing vector

will the reversing vector just work same as reversing an array using this->array ? *misread "reserve" as r
2/2/17

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Instr Extreme Edge Cases Assignment Feedback

Here is the feedback that we got for Extreme Edge Cases (https://goo.gl/forms/z06gBY7MocFDrE3S2): How clear were the doc
- An instructor thinks this is a good note
2/2/17

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How to write test cases for document.c?

how am i going to provide files for it to test?
2/2/17

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Vector push back

Adds a new 'element' at the end of the vector, after its current last element. This effectively increases the co
2/2/17

0
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Env doc clarification

Each reference to <srcvar> should be replaced with the value of <srcvar>. I want to make sure I'm unders
2/2/17

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Setting at position larger than size / capacity

For example, if my size is 5, is it allowed to set a value at position 7? Is it also allowed to set values at positions
2/2/17

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docuemnt_create_from_file

Hello, I have a question about the function create_from_file in the document.c. According to the description, we
2/2/17

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path_to_file and fopen

Hello, I am wondering for the document.c file of the vector MP. Can we use fopen directly with the path_to_file
2/2/17

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angrave's old lecture handouts?

anybody know where to find those?
2/2/17

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Contiguous data...?

The spec in vector.h describes vectors as holding its data elements in contiguous memory locations (presumably for bette
2/2/17

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How to Use Function Callbacks?

Hello. In the first portion of vector.c, there are a bunch of function callbacks in the vector struct. I did some googli
2/2/17

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if argc < 2

Should we print out anything if argc <2 ? I've just exit(1) so far.
2/2/17

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what does the colon mean in here?

./env PATH=%HOME/bin:%PATH,IDIR=/%HOME/include,LIBDIR=/%HOME/lib make -j4 I didn't understand the colon in here, s
2/2/17

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pid == -1 vs WIFEXITED(status)

If waitpid(child1, &status, 0) returns -1, is that the same as saying WIFEXITED(status) returns false? The example i
2/2/17

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File handler in child process

In the wiki book, the last section says both parent and child process share the same file descriptor. But I am confused
2/2/17

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running env without arguments

In the lab description, we are told When run without arguments, it prints a list of all the current environment variabl
2/2/17

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Calling Default Constructor

How can I create default object? If the memory location is x, should I just say x->default_constructor?
2/2/17

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Allocating memory for vector

When we're allocating memory for the array of pointers in the struct, do we also need to allocate memory for the act
2/2/17

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env: support values with spaces?

The official implementation of env supports setting environment variables to values with spaces in them by surrounding t
2/2/17

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Lecture recording is down?

When I was trying to go over some of the lecture videos, it shows that the web page might be temporarily down. When can
2/2/17

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Handling Problems in Time Function

Should we print anything if exec or fork fail in our time implementations? The lab page says If the program does not te
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2/2/17

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ssh connection closed

I get "connection closed by 172.22.152.81" whenever I tried to ssh on my VM,with vpn already turned on. I also t
2/2/17

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vector_insert()

For vector_insert(), what should we do if the user attempts to insert into a position >= v->size? Should I have an
2/2/17

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Potential Overflow Issue in Elapsed Time?

I've been trying for quite a while to get my time implementation to return the correct time when computed precisely.
2/2/17

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vector_create() confusion

As I understand, all the three parameters are pointers to function. However, how could we copy a vector without a pointe
2/2/17

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Instr Extreme Edge Cases AG Rerun

Hello everyone! We realize the final ag run may seem unfair, and we are here to alleviate some concerns. 1) The reaso
- An instructor thinks this is a good note
2/2/17

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After reading wiki for exec, still unclear

I am trying to call execl("sleep", "sleep", "2", (char*)NULL); But it still fails. Any change?
2/2/17

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Mystery Camel Case Functions

After the submission deadline will we be able to see what the mystery function test cases were? I'd like to see what
2/2/17

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spent hours on lab2 and got -4 in the end. Should I drop the course?

looking for advice.
2/2/17

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Function 1

I just want clarification as to why I got a -6 for the first function since I spent so long on this lab. If I am to unde
2/2/17

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LOL

Got 23/25. Spent hours trying to get 25/25. Was pretty sure that I would get it, since I finally found a subtle bug in m
2/1/17

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Lost on Vector MP

I've been reading through the documentations but I feel like the more I read, the more I don't understand what i
2/1/17

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Vector_resize interpretation

Let's say we have a vector with three elements in it. Then I call vector_resize(this, 5). Now the vector has five el
2/1/17

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Instr Utilities Unleashed!

We have released the Utilities Unleashed lab. This lab is located in your svn repo at: https://subversion.ews.illinois
- An instructor thinks this is a good note
2/1/17

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copy_constructor_type confusion

Is copy_constructor_type a structure I should define? How could I use a structure like a function? Thanks.
2/1/17

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insert and erase function

Hi, I have questions about the vector MP. I noticed that in vector.h file, we are given the instruction to relocate
2/1/17

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Case of "abc"

Hello all, I'm bit confused right now so I want to make sure. Say if we type "abc" (without any punctuation)
2/1/17

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What to do with ascii, graph, control etc inputs

So my current final loop for storing the camel case string involves checking if its alnum and if so then storing it in t
2/1/17

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Vector clarification

1) Why does the picture here get removed from the MP webpage @325? 2) Let's say I have an array lis this [NULL
2/1/17

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Instr Autograder MP Vector Released!

Vector AG has been launched! Schedule: "2017-02-02 22:00", "2017-02-03 22:00", "2017-02-04 22:00&#
- An instructor thinks this is a good note
2/1/17

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camelCaser '\b'

Does the autograder test things with '\b'? If it does, should the output of "some thing\b." be stored a
2/1/17

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Type of data and arguments

How do we know what type of data the user is asking for? I see that each type of data calls the vector_create() passing
2/1/17

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Test Cases

I got 6/9 on my camelCaser implementation, if I write test cases that my function fails will I lose points on the implem
2/1/17

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CamelCaser reference

My friend and I both ran the camelCaser-reference for the following input: \a 3f. \a3F.\n\t\v55R 55r. 123 123456789e.
2/1/17

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How to handle input without punctuation

If we call this for example: output = camelCaser(" "); Should camelCaser return a NULL pointer? Or should it
2/1/17

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6 pm autograder

Has the 6 pm autograder run yet? I've been refreshing the page for quite a while now but I see no changes.
2/1/17

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vector_set input

In vector.h, before vector set function, the document states: /** * Sets the 'element' at position 'n'
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Test Case Syntax

Running into an issue where I'm passing every test function except for Function1. In my testing I've realized th
2/1/17

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Function 1

I have seen the other posts regarding function 1; however, none of them honestly seem to be too helpful. There's so
2/1/17

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Finding the number of bytes in realloc

According to the man pages, "the realloc() function changes the size of the memory block pointed to by ptr to size b
2/1/17

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Vector Size vs Capacity

I just wanted some clarification on the size and capacity properties of the the vector struct. The MP documentation say
2/1/17

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Odd Reference Behavior

> \b 114f GIRAFFE. \\ will it. { 114FGiraffe", "", "willIt", NULL } > 114f GIRAFFE. \\ will i
2/1/17

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Segfault on my camelCaser for adding unit test case specifically for "..."

Should I still add it to grade the other "interns code" or could this mess up my program while its being graded.
2/1/17

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autograder test

the output of ./camelcase, whether success or fail, is just a indicater that our own function is not 100%perfect(cannot
2/1/17

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I failed all the unit-test that would lead to a negative grade

I failed all the unit-test that would lead to a negative grade except function 7 and the testAscii. But I pass all the o
2/1/17

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Different output

I got this when I tried to compare string : a a nnn aFAILED but I got printed these strings out when I dont compare th
2/1/17

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16 inputs 128 chars

I've read the other piazza posts and am not clear on this. The documentation says that "you may not try more tha
2/1/17

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Memory leak when testing " "

I got no memory leaks for all test cases except when testing " ". When I set input = " ", I got m
2/1/17

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Valgrind Fatality

I am getting this Valgrind message and I don't know what to do: valgrind: the 'impossible' happened: Kill
2/1/17

4
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Output keeps changing

Hi, My terminal output keeps changing without any changes to the code and I have no idea why. I began with testing a
2/1/17

2
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it this a bug in the reference.

it this a bug in the reference. input: a\bN a\bbcd. output: nbcd. shouldnt it be "nBcd"?
2/1/17

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Is there a credit for trying?

I made separate functions of removing the blank, performing camel case conversion, splitting into arrays and they all
2/1/17

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gdb problem

When I am running gdb and step to free(*ap), I get an error like this: __GI___libc_free (mem=0x603500) at malloc.c:2932
2/1/17

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Process Control Question

int status; pid_t child = fork(); if (child == -1) return 1; //Failed if (child > 0) { /* I am the parent - wait for
2/1/17

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test case function1

So I keep failing function 1. I wonder should we test \n \t in our test case? since I've done that, and maybe it
2/1/17

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HW0 Grade

When can we check grade for HW0? Knowing what I got wrong and taking time to fix my knowledge holes will be super helpfu
2/1/17

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Test Function 4?

Somehow, through all the modified tests and everything I've been able to think of and do to test the camel caser, I
2/1/17

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If there are no sentences (no punctuations) in an input string..

Do we return NULL or an array which has one element which is NULL? Or is that essentially the same thing?
2/1/17

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Any more autograder runs today?

I mean before the deadline at midnight? Please and thank you :D
2/1/17

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Autograder Question

I was passing Function1 but failing the rest of them Function x test cases, but now i fail function 1(-6/6) but passing
2/1/17

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Whats the course policy on retakes on Labs?

Do you you get to redo two lab/mps at the end of the semester?
2/1/17

2
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how are two .cfiles graded

cc.c and cc-test.c are graded seperatedly or combined? That is to say, if my own ccfunction cannot pass one of the testc
2/1/17

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String with no punctuation at all

Hi, if the input is abc should the returned (char**)output output == (char**)NULL or output[0] == '\0' output[1]
2/1/17

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Weird AG Result Change

Hi, I previously passed all function 2-16 but failed function 1. But after I provided more test, fixed some memory leak
2/1/17

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Output Question

I am confused on what our output has to look like with our own test cases. When I use the reference command, it outputs
2/1/17

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Does It Matter If Documents Store Newlines Internally?

Currently my Document implementation stores \n in it's vector entries, but I was wondering if for the sake of future
2/1/17

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Function1 vs. Function2-11 testing

Last AG run, after modifying my code, I got all the Function tests correct except Function1. Before I got all the rest o
2/1/17

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reference question

when I typed "\b." the result is { ", NULL} Do we have to consider such cases as \b starts the string?
2/1/17

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Reference bug?

When I input "1 2 5q6.", it output ["125Q6", NULL]. Shouldn't it be ["125q6", NULL]?
2/1/17

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ASCII Implementation Failure

I've been putting a lot of effort into trying to get my implementation to pass the ASCII test on the auto-grader. So
2/1/17

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outline for test.c

on on hand, it says " demonstrate to the head honcho at Facenovel exactly how robust your own function is", on t
2/1/17

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Function Pointers for the Vector?

How do you instantiate a new vector with function pointers to the appropriate constructors and destructors? The followin
1/31/17

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autograder is not running tonight?

Hello, In the previous Piazza post, it says that there is going to be auto grader run trails tonight. Bu
1/31/17

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How does splitting work?

I successfully implemented functions to remove the space and perform a basic camel case conversion for a sentence, bu
1/31/17

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How to account for empty sentences

I use strtok, and if there's nothing between two punctuations, I can't think of any way to account for the exist
1/31/17

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camelCase-reference output

When I put test test test into the reference function I got { NULL} as the result. I'm really confused. Shouldn&#
1/31/17

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22:00 AG run?

That apparently hasn't happened yet... Any updates?
1/31/17

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Malloc Double Pointer

From what I understand, by doing char** double_ptr = malloc(MY_SIZE); we are allocating MY_SIZE space for the array of p
1/31/17

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camelCaser-reference result

When I plugged the string WHERE title = ’Star Weirs’ AND producerC# = cert#; in camelCaser-reference, the result was {
1/31/17

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Wrote on un-writeable file

I accidentally on purpose changed the main file in camelCaser, is there any way to retrieve the old file?
1/31/17

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MEmory

Will we be taken points off if we have memory leaks?
1/31/17

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AG at 10 and at midnight?

Does the AG run at 10pm tonight as well as midnight?
1/31/17

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\n

does \n count as a space? When I run hello \n world with camelCase-reference I get: { "helloWorld", NULL }
1/31/17

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Should pointers to entries have their own spaces in the heap?

My understanding is that: Elements [0, size) of vector->array are pointers to heap memories (entries stored in the ve
1/31/17

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comparing array of strings

Is there a more efficient way in c to compare an array of strings other than just iterating through both arrays and comp
1/31/17

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Help! camelCase not working when run multiple times

Hello. My camelCaser outputs correctly when I run one input test string at a time. But when I run 3, this outputs: YOUR
1/31/17

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Clarification on NULL termination

So in the very last element for our char** do we store a pointer to NULL? Or just NULL? for example char *ptr = NULL; r
1/31/17

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reference camel

I'm trying to check with the ./camelCase-reference but it keeps returning NULL whatever my output is...
1/31/17

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camel_caser_test.c

Just making sure if this is what we are supposed to do for camelCaser_tests.c int test_camelCaser(char **(*camelCaser)(
1/31/17

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Weird error with null pointer at the end.

I'm getting this error when I assign to output_s[j] when the size of output_s is j+1: ./camelCaser camelCaser:
1/31/17

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Question about ASCII characters

My implementation passed all the test cases, but I'm not sure if that's correct. Let's say I have a string &
1/31/17

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New Reference newline behavior

So, in the new reference camel caser, if you enter: this is \n a test. It will camel case it like: "thisIs", &
1/31/17

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Instr New Extreme Edge Cases Ref

Hello! We've updated the reference to handle escaped characters such as '\\', '\t', '\n', e
- An instructor thinks this is a good note
1/31/17

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special characters \n \b \0 in string

I have no idea how to pass those special char in terminal in order to try out the reference. Also when I try something
1/31/17

3
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Office Hours TA?

It's currently in to the 5pm scheduled office hours, and there has been no notification that the course staffer coul
1/31/17

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malloc

Is there anything wrong with allocating too much memory? For instance, if I want to allocate memory for an array of stri
1/31/17

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Are we allowed to printf()?

For extreme edge cases, are we allowed to leave debugging lines line: printf("Failed due to long strings"); in
1/31/17

8
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To delimit with strtok() the punctuations

could I just include all the punctuations in the delimiters. for example could I do for all the punctuations. // char *
1/31/17

7
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For loops not executing in my program???

For some reason I cannot get a single for loop to run in my program. I've been debugging through gdb and when step t
1/31/17

4
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free memory in test case

So I free all memory in testcase function. When I test my own code, I know what pointers have to be freed, but when test
1/31/17

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Output looks correct..

When I print my result manually, it looks correct, and it is NULL terminated. However, when I use camelCaser_test to tes
1/31/17

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Regarding camelCaser_tests.c

Just to confirm, in camelCaser_tests.c we should give the functions we're testing 16 different strings and diff them
1/31/17

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Assigning NULL to pointer is giving errors

Hi, I hope this question isn't dumb and if not, hasn't been asked already. (I really tried to search myself.) An
1/31/17

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when not running on gdb, it sometimes fails

Hi. My program sometimes fail when I run by executing the exec. file on command line. However, when I run it in gdb, it
1/31/17

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Newlines in Extreme Edge Cases

In order to understand the expected output of control characters in the input string, have an input.txt file and feed it
1/31/17

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Input is too long!

My code passed every unit test yesterday. However, my code failed every unit test on "2017-02-01 12:00" 's a
1/31/17

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test_camelCaser

int test_camelCaser(char **(*camelCaser)(const char *)) Can someone explain to me this line? I understand that camelCas
1/31/17

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study group

Hi, To be better prepared for this class, I am looking to form a study group for discussing code, reviewing materials,
1/31/17

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svn tree conflict

When I try to svn from EWS machine (not in vm ) I get a tree conflict , and when I do svn status, all files status is D.
1/31/17

26
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Instr Extreme Edge Cases Autograder Update

Hi everyone! We re-ran the autograder for Extreme Edge Cases and updated it to provide some more helpful logging output
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1/31/17

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Difference between vector_front and vector_begin

There is a slight difference between vector_back and vector_end, but vector_front and vector_begin are same. Am I right?
1/31/17

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vector_create()

I've the doc but still don't fully understand why we pass copy_constructor, destructor and default_construct int
1/31/17

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Should I consider any control character in ASCII?

Hi everyone. I will be appreciated if anyone can tell me whether I should consider control character in test case even t
1/31/17

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Punctuation

":)^+-*/\|=&%$#@" Are this supposed to be treated as punctuation? Should we include these in our tes
1/31/17

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Problem with freeing pointers and

There are some pointers in my camelCaser.c that I cannot free without causing the program to crash. Is it ok if I free t
1/31/17

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Extending Vector (pushback)

I suppose that for a vector like the following: [ 1, 65, 2, NULL, 1234, NULL, 12, NULL, NULL, NULL, NULL, NULL] a pushb
1/31/17

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Committed to svn, but change not showing up online

I committed my final code to subversion before the deadline, but for some reason, it's not reflected online, and the
1/30/17

1
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Plagirism

Hi, Is it considered cheating if I copy my mp or labs from the previous semester? (I know CS 233 lets you but want to m
1/30/17

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unit testing

Hi, I'm sorry if this sounds like a bad question, but I'm pretty confused about the unit testing part of the cla
1/30/17

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Process sorting algorithm

Hello, In today's lecture, there is a program demo that could sort numbers. #include <fcntl.h> #inc
1/30/17

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Can we print anything in unit tests?

I added a few test cases but still got -6/6 for Testcase function 1. I wonder if this is because I printed my output for
1/30/17

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Function one test?

So, I am passing every single test case that is provided, except for Function 1, where I am getting -6/6. Is there any i
1/30/17

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Fail most of the test cases

Before this AG run, I passed most of the test cases. However, after adding a few new test cases and test them on my end,
1/30/17

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do not have today's grade report in my svn

I wonder if the autograder has run today because it should be run at 10 but I still do not have today's grade report
1/30/17

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Extreme Edge Cases memory leak?

So, I am consistently failing function 1, and I believe it's due to leaking memory if the function is not valid. How
1/30/17

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Interpreting autograder output

I got -6/6 on Testcase: Function1. The output is: Trying to compile your code... Successfully compiled your code.. Fail
1/30/17

2
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should number be in the string?

isalpha() return false if I check numbers, but when I use reference, it also print out numbers as strings. So should I a
1/30/17

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Mount Point?

I am trying to set <code>sudo sshfs NETID@sp17-cs241-???.cs.illinois.edu:/<MOUNT_POINT> ~/remote </
1/30/17

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const pointer

so if argument passed in is a const ptr, why I cannot assign ptr2 = ptr and change ptr2?(like ptr2++) in the fun
1/30/17

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Invalid write

what could be some possible reasons if valgrind complains "invalid write of size 1" and "invalid write of si
1/30/17

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Should a empty row be NULL or something else?

In the reference program, if I type in something like : "a..a.", it will give me { "a", "",
1/30/17

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LAB2 camel_case

I'm trying to access all the characters in a char**. I have some code that looks like (result[j] +(int)k) = &am
1/30/17

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What's the deal with backspace

Let's say I have something like this: "5 \b2world!" What should the output be? I can't use the r
1/30/17

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lost on the test case part

So I'm a bit lost on how to write the test cases in the test_camelCaser function. Do we use the **camelCaser argumen
1/30/17

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strange_step

How exactly do I set the value of a char to be particular number lets say 15 at that location? I understand that this st
1/30/17

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Use of copy constructor in Vector MP?

So, I'm looking at the functions we are supposed to implement for the Vector MP, and I don't see when we would e
1/30/17

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Weird Valgrind Output

--18808-- REDIR: 0x401cdc0 (ld-linux-x86-64.so.2:strlen) redirected to 0x3809e181 (???) --18808-- Reading syms from /usr
1/30/17

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Valgrind

Valgrind's saying that I've definitely leaked memory, but it doesn't show a stack trace to help me identify
1/30/17

4
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part 2: 12 functions?

Well, I just noticed that on website its said that there are 12 functions in .c file and we have to use all of them, But
1/30/17

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autograder for mp1

I check the grade report(today's noon). I find it is same with the grade report in yesterday. I believe I do fix the
1/30/17

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Multiple Punctuation Autograder

My own camelCaser passes every test except this one on the autograder. I've thrown everything I can think at it and
1/30/17

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ImplementationASCII

Hello, I hope everyone has had a great day. I check my lab report and found out I failed the ImplementationASC
1/30/17

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part2-heap

When is it necessary to create malloc when declaring char* in our main function? In my part2, I directly assign most of
1/30/17

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Instr Monday 10-11am OH cancelled

Hi everyone, I'm currently out of town and cancelling my office hours this morning. Sorry for any inconveniences -
1/30/17

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ASCII question

For example, should we consider '\t' as a tab character, or as '\' and 't' separately? If we co
1/30/17

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Where can I download the handout of last friday's lecture?
1/29/17

2
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Question about part2 autograder

Hi there, Is that anywhere for we to know which function are we doing wrong on pointers_gone_wild part2 testcase? Cuz m
1/29/17

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No memory test and testcase test for lab2?
1/29/17

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return null or pointer to null

If input string is NULL, just return NULL; If input string is white spaces, return a pointer to NULL pointer. Am I right
1/29/17

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strdupa

The compiler gives me no warnings of implicit function declarations, but on the autograder it tells me strdupa is implic
1/29/17

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Does returning array guarantee to be null terminated?

I see that there is a test case called implementationNullTerminated. Does the returning array of strings guarantee to be
1/29/17

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Bad grading?

Why is this -6/6 rather than 0/6? This is for extreme edge cases.
1/29/17

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lots of mallocs?

when we make our char ** array to return from the function, we will malloc space for the array, and for each string poin
1/29/17

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Skipping Tests

Any particular reason that the EEC tests skip around? For example, my grade report didn't run tests function[4, 7, 8
1/29/17

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diff checking mp1

Hi, how can I diff check my part1 output? It seems there's no output file created in part1-main.c
1/29/17

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finite automaton

Hi, I don't quite understand how the output of the automaton function is printf("%d\n", little_automaton(tr
1/29/17

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Valgrind Issue

nvm
1/29/17

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Anyone else with Mac able to double ssh?

I tried using ssh into the workstation and then into the VM with '-Y' but it wouldn't let me open anything w
1/29/17

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output result

is it fine to output the following: == two() ==20 not passed!100 passed! ------------------------------------- in the so
1/29/17

1
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What is the highlight '%' in the end of the line?

Hi, When I run #include <unistd.h> /*fork declared here*/ #include <stdio.h> /* printf declared here*/ in
1/29/17

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nvm

nvm
1/29/17

1
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Instr Vector Released!

We have released the vector MP. This mp is located in your svn repo at: https://subversion.ews.illinois.edu/svn/sp17-c
- An instructor thinks this is a good note
1/29/17

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No grade_report.html in Lab 2

There is no grade_report.html in my Lab 2 repository. And when I open the link in the email https://subversion.ews.illi
1/29/17

2
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Instr Autograder Lab Extreme_Edge_Cases Released!

Extreme Edge Cases autograder is out! Please check your grade at: https://subversion.ews.illinois.edu/svn/sp17-cs241/YOU
- An instructor thinks this is a good note
1/29/17

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list of all printable characters which are not spaces or alphanumeric characters?

I hope that I could use strtok but I have trouble listing all these characters. by the way string !"#%&'(
1/29/17

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Using c99

Are we allowed to include <ctype.h> to use C99 in the mp's?
1/29/17

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NULL characters input

The reference says "\0 Hello World." should return: "" helloWorld NULL Im having trouble trying to figu
1/29/17

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Different output in function two?

My program is printing out == two() == 20 not passed! 100 passed! but, the actual output is supposed to be == two()
1/29/17

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the_end function question

void the_end(void *orange, void *blue) { if (orange != NULL && orange == blue && ((char *)blue)[0] == 1
1/29/17

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Weird output results in mp1.

I'm getting the right results when I open my part2( the output of my part2 code) file using "open part2" on
1/29/17

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strange_step

void strange_step(char *value) { if (*(int *)(value + 5) == 15) printf("4: Illinois\n"); else pr
1/29/17

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Lecture Recordings Down?

Are Lecture recordings currently down? https://recordings.engineering.illinois.edu:8443/ess/portal/section/bdaf2970-ca83
1/29/17

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Question about MP1 tok_step

void tok_step(char *str) { char *a = strtok(str, ","); a = strtok(NULL, ","); if (strcmp(a, "
1/29/17

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Code uploaded to svn but not used in Autograde?

I had this issue with the lab last week but thought maybe I just forgot to upload my code until late, but this time I ca
1/29/17

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Are we going to get autograder runs for every single MP and lab before the deadline?
1/29/17

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gdb optimized out

When I use gdb try to print out some variables, it shows : <error: value has been optimized out> what's the
1/29/17

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finding compiler error

this might be irrelevant but I've been getting this complier error warning when I do 'make' command and I c

▾ Week 1/22 - 1/28

1/28/17

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Part2-11

I've been stuck on this for almost the last 2 hours. I was thinking that it had something to do with how ascii chara
1/28/17

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"" == "\0" ?

When I put [..] into the reference, I got "" "NULL" these two return values. Are "" and NU
1/28/17

2
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camelCaser-reference

When I input "241cs, cs241", camelCaser-reference returns "241cs", NULL I am wondering why the "
1/28/17

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Return Error

For some reason I get an error saying I can't return my char * from the stack? Why does it complain about this? Scre
1/28/17

6
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Failing test 8

Hi, I'm failing test 8, even though it compiles and the output looks correct.. I diffed the files and there is a di
1/28/17

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Thirteen segfault

My function for thirteen is behaving strange, it produces the correct output but occasionally it segfaults. If I run ./p
1/28/17

5
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Test cases and reference clarification

1. I've been writing helper functions in my camelCaser_tests.c (e.g. there's one function to test for white spac
1/28/17

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Number of mallocs

"Note that all the C strings must be in their own buffers (1 malloc per camelCased sentence)." I assume this mea
1/28/17

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Via array index vs asterisk

Let's say I have char **output = (char**) malloc(sizeof(char*)); If I do output[0] = "hello";vs.*output = &
1/28/17

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pointers as parameters in functions

void strange_step(char *value) { if (*(int *)(value + 5) == 15) printf("4: Illinois\n"); else pr
1/27/17

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possible wrong outputs by camelCaser-reference?

Hi. I was just playing around with camelCaser-reference and my custom made one (camelCaser.c) to compare my answer with
1/27/17

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CamelCaser Testing Segfaults

Are camelCaser tests allowed to segfault for "bad" camelCaser implementations or should test cases defend agains
1/27/17

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initializing a string-valgrind error

valgrind gives me an error with this code char * value = malloc(sizeof(char)*9); that I am using an uninitialized valu
1/27/17

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Root access to EWS or VM?

I'm a bit confused on whether we have sudo access to install anything on our EWS machine or just in the CS 241 VM?
1/27/17

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Why do I get this??

10: Illinois==28935== Conditional jump or move depends on uninitialised value(s)==28935== at 0x40081E: the_end (part2-fu
1/27/17

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GUI's extremely slow on personal machine

Hello. I am SSH'd via Putty with Xming to my 241 VM. This is on my personal Windows computer. The issue is that when
1/27/17

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Changes to Friday office hours?

I was the only person on the queue today for 1-2pm office hours, the TA on duty was there earlier in the hour but around
1/27/17

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How to test test_camelCaser.c

I wrote a few test cases for test_camelCaser(), but how can I test my test_camelCaser function? I see in the main functi
1/27/17

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Execlp example

In the wikibook, it said that this example does not work: #include <unistd.h> #define HELLO_NUMBER 10 int main()
1/27/17

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Printing to stdout/stderr

Will the autograder care if we print to stdout/stderr (assuming that the memory structure returned is still correct)? Or
1/27/17

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array of char pointers terminated with NULL

Hello, Let's say we have an array of char** a. What does it mean to make it null-terminated? Does that a+
1/26/17

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When is MP2 Going to be released?

Website is saying MP1 is due Week 3 and MP2 is realeased Week 3. Will MP2 be released this Sunday (1/29) or next Sunday
1/26/17

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diffing with expected output?

How would we diff the output of our program with the given expected output?
1/26/17

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Instr 241 Schedule Chart

Dear CS 241 Students, Luke Liu has made a cool chart for the class at the bottom of the schedule page: http://cs241.cs
- An instructor thinks this is a good note
- 1 Unresolved Followup
1/26/17

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MP1 part2.c Weirdness

Something weird is happening. I completed the three_step() function in part2.c and got the expected "7. Illinois
1/26/17

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lab 2: can we malloc in camelCaser.c?

In the docs, it says "camelCaser.c may not leak any memory", so can we still use malloc() in camelCaser.c and fr
1/26/17

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Is it possible to write a good test case in less than 16 inputs?

Hello everyone, I am wondering that how various could the function camelcase be for testing pu
1/26/17

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mp1 function six

int main() { float *p_six; int i4 = 4, i432 = 432; p_six = six(&i4); printf("%d == %f\n", i4, *p_six); free
1/26/17

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Lab2: Test non-null-terminated output

Suppose my test function is given an output with wrong length (number of sentence), and it is not null terminated. Is th
1/26/17

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Keyboard command to log someone out of EWS?

I have tried CTRL-ALT-BACKSPACE CTRL-ALT-DELETE CTRL-SHIFT-BACKSPACE but nothing's working. I really need to use t
1/26/17

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Lab sections

Can we leave the lab section if we are done with the worksheet, lab, and MP?
1/26/17

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Testing Documentation

In the "Writing Unit Tests" section of the extreme_edge_cases docs, it says: Also it is not in the spirit of uni
1/26/17

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autograded time?

I finished and tested several problems in MP1 last night. It compiled well and gave me the desired answer. However, the
1/26/17

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how to concatenate character to string

how to concatenate character to string
1/26/17

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Chara Gradebook

When will the Chara Gradebook be activated? Or is it already and I'm just missing something?
1/26/17

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Instr Autograder MP Pointers Gone Wild Released!

Pointers Gone Wild autograder is out! Please svn up to get your autograde reports. You may also check your grade at: ht
- An instructor thinks this is a good note
1/26/17

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Modifying camelCaser_test.h

Are we allowed to edit camelCaser_tests.h to add helper functions and/or separate our unit tests into multiple functions
1/26/17

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MP autograder starting anytime soon?

When could we expect the first run?
1/26/17

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Instr Use EWS/Local Machine & SVN

We might experience VM issues these next few days. We've pushed a new makefile to your svn for pointers_gone_wild t
- An instructor thinks this is a good note
1/26/17

1
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Instr extremeEdgeCases Debugged!

Dear CS 241 Students, We have released extreme_edge_cases! Documentation can be found here : http://cs241.cs.illinoi
- An instructor thinks this is a good note
1/26/17

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weight for each lab and mp

I know that the grading percentage of lab is 13 percent and mp is 25 percent, but is there specific weight for each lab
1/26/17

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usage of fork

I don't quite get when we have to use the fork function. I know it is defined as a function that creates a new proc
1/25/17

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type mismatch?

in wiki book, I saw this piece of codechar *ptr = "ABCDEFGH"; int *bna = (int *) ptr; bna +=1; // Would caus
1/25/17

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Switch versus if/else

For function fourteen in part 1 of the MP, are we allowed to change the switch to if/else statements? Or do we need to k
1/25/17

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codes submitted to svn look different on mobile phone

I have submitted shred.c with revised version, and that submitted codes in svn look the same through my laptop, but thro
1/25/17

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Extra byte being added twice?

In shred.c, the write random function has it so that it checks the min of page size and num bytes +1. I am assuming
1/25/17

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function 18

/** * Manipulates the input parameter (k) and prints the result. * * @param k * The input parameter to manip
1/25/17

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Autograder gave full credit despite final.txt and final.orig.txt

Hi, I ran stat to see the size of my files after shredding, and this was my output: The file size before shredding
1/25/17

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final.txt wrapping

Not sure if this is relevant to the testRandomBytes test case, but does final.txt after mangling the file need to be wra
1/25/17

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Pointers gone wrong

when the code says (int *)(value + 2) is the plus two applied to the original char pointer value first or is it cast
1/25/17

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How to increment memory address?

is ox75dddd0+16=0x75ddd16?
1/25/17

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Personal email ID?

I am not receiving a copy of my hw0 on email if I use my illinois ID. My personal sends me one however and includes my f
1/25/17

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Odd Memory Leak - _IO_file_deallocate

So, I've passed all the test cases and eliminated a memory leak in shred.c (spoilers for those who haven't done
1/25/17

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address wrong?

Let's say that we declare a pointer int *ptr. For the sake of discussion, let's say that ptr points to memory ad
1/25/17

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file not found

when I run gdb, I got [Inferior 1 (process 21922) exited normally] not like many others get segfault somewhere. How can
1/25/17

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STDERR_FILENO

What's so special about STDERR_FILENO? It seems to do the same thing as STDOUT_FILENO when used in write(STDOUT_FILE
1/25/17

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autograder for mp1?
1/25/17

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urandom generating too large of chars?

While checking the document statistics in gedit, I've noticed that urandom is giving me chars that are more than 1by
1/24/17

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memory leak

After running Valgrind, the memory leak was traced back to the following statement below but I am not quite sure what si
1/24/17

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HW0 Question

On HW0, in regards to the following question: "Write a program that uses write() to print out a triangle of height
1/24/17

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getting correct(?) answer without changing anything - Lab1

I tested the original code by doing $ make reset # Make sure to do this before test cases $ make $ ./secure_move files/
1/24/17

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Exams and Quizzes schedue

Do we have a (tentative) schedule for exams and quizzes yet?
1/24/17

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TestUsage, Test cases with 0 total points

Should we aim to get "1/0" points on test cases like testRandomSize? What does testUsage: "Test invalid comm
1/24/17

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'iostream' file not found

compiler complain that count is unidentified and I tried to add #include <iostream>. However, it turns out iostrea
1/24/17

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Instr CS 241 Assignment Evaluation Form

Dear CS 241 Students, We strive to provide the best assignments that we can for this course and would like your feedbac
- An instructor thinks this is a good note
1/24/17

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I've submitted my HW0?

I have not gotten an email. What did I do wrong? I've used my personal email and I received one, however if I use my
1/24/17

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Garbage characters in final_out

Whenever I run secure_move, I keep getting these garbage characters in my final_out. I havent changed anything else (my
1/24/17

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svn submission

In the first lad, it seems like we just need to commit our modified code instead of adding any thing to commit. Will thi
1/24/17

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Question about using undeclared function

Hello, I was reading the wiki book and ran into this section:I am confused about how it works. If you do not pr
1/24/17

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This assignment must be compiled on the CS241 VMs. Stop.

Can somebody help me from this? I went to any of the place with ews computer, but it does not work. What is the problem
1/24/17

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GDB system calls

How do you break out of called functions or system calls in gdb?
1/24/17

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So after testing secure_move on final.txt to final_out.txt I get the following results.

-final.txt is mangled up with random bytes entirely -final_out.txt and final_sol.txt are the same with the diff command
1/24/17

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Instr Honors Section Scheduled!

If you are registered for the honors course or are interested in joining, we will be meeting from 6-6:50pm on Tuesdays i
- An instructor thinks this is a good note
1/24/17

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MP1 Question

== two() == 20 not passed! 100.000000 passed! Should it be 20.00000, or is the above specification fine?
1/24/17

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How to sign up for auditor？

Hi, I can't register this course because of time conflict. May I ask how can I sign up for auditor？
1/24/17

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Cannot open files anymore

After my last commit, I am no longer able to edit my files in emacs. When I try to open them, I get the following error:
1/24/17

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When will the MP autograder runs begin?

I know it's a bit early but I really appreciate being able to assess progress by looking at nightly autograder resul
1/24/17

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Confusing about autograder

The autograder is at 10 pm yesterday and I found I got 0/2 at 11 pm. I did not submit again but found I got 2/2 this mor
1/24/17

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Clear_bits function

Not really sure what the description means: /** * @brief * Clears the bits in "value" that are set in
1/24/17

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file that is secure_moved from is supposed to mangled with random bytes, when I checked my final.txt

My final.txt is filled with random bytes for one third of the file. Is the entire file supposed to mangled?
1/24/17

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The autograder timestamp is the time the reports are released and not the time ag is ran right?

For example, if the autograder ran on the 21st and 11:59pm the timestamp for 2017-01-22 00:14:12.945813 is actually the
1/23/17

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How to restore original code

I commit some wrong code. I want to restore the how lab to its original state. How should I do this? I tried to delete e
1/23/17

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Something interesting

Just kinda something interesting i found on accident if anyone wants to try it: I had caps lock on by accident when i sw
- An instructor thinks this is a good note
1/23/17

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Final.txt

when I committed my latest changes to SVN, final.txt also changed. should that affect my autograder report? the result o
1/23/17

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Question about Valgrind

If I run valgrind ./secure_move-debug files/final.txt files/final_out.txt It outputs "definitely lost: 29,406 byte
1/23/17

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File not found return value

Should we return a specific value for input file not found?
1/23/17

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Angrave's old Lecture Videos

Does anybody know where we can find the links to Angrave's old lecture videos for extra review?
1/23/17

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VM question clarification in Chapter 2.3

In the question of "sizeof character arrays, incrementing pointers" Can you use print("%c %d\n", *ptr, *
1/23/17

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MP and lab links not working

I tried to open the links to the assignment prompts on the class website and it says "this is not the webpage you
1/23/17

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gedit on putty ssh

i tried to use gedit on the putty ssh (im using windows), but the gedit doesnt work. The TA in the lab session told me h
1/23/17

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A Pointer casting problem.

char *whatever Suppose I already had a char pointer. Can anyone answer what is the difference between *(int*)whatever an
1/23/17

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Variable is optimized out

I set a breakpoint in read_wrap.c to check if the value of wrapped_string is 80, but when I print the variable, it says
1/23/17

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When will yesterday's autograder results be released?

I would like to know whether my changes were beneficial or not.
1/22/17

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Using Putty with CS241 VM

I am using Putty along with Xming (for X11 forwarding) to access the VM for this class. I was wondering if anyone knew h
1/22/17

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Instr Tutorials Galore!

Hello Eager Students, We have heard your requests for tutorials and have started developing them! If you go to http://
- An instructor thinks this is a good note
1/22/17

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Submit debug compiled?

What compilation should we submit the Lab with? Make/Make debug? Should the executable be secure_move or secure_move-deb
1/22/17

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malloc question

struct Link{ int value; struct Link* next; }; typedef struct Link link_t; link_t one; int value; int main() { lin
1/22/17

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Instr Honors Section Tentative Schedule

For those of you registered for the honors section or interested in joining, we will be (tentatively) having our first l
- An instructor thinks this is a good note
1/22/17

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This assignment must be compiled on the CS241 VMs

When I try compiling the first MP, I get the error message in the title. Is there a reason why compiling this assignment
1/22/17

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Instr Pointers Gone Wild Dereferenced!

Dear CS 241 Students, We have released pointers_gone_wild! Documentation can be found here : https://illinois-cs241.gi
- An instructor thinks this is a good note
1/22/17

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can't open the link in the Configuring Putty part

https://security.illinois.edu/content/ssh-windows I'm using windows and I can't open the link(this picture) in C
1/22/17

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how does read() work?

I tried to used gdb to debug testRandomBytes. I searched it on google and it says read() will return the number of byt
1/22/17

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How to compare number of bytes?

Hello. For testRandomBytes, my understanding is that we need to ensure final.txt and output.txt have the same number of
1/22/17

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print size of array with gdb

if I have a variable char* buffer, how do I use gdb to print out the size of "buffer" in bytes?
1/22/17

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testRandomBytes

For testRandomBytes, are we supposed to keep the size of the final.txt the same as it was before we overwrite it? Is it
1/22/17

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Instr Autograder Lab Know Your Tools Autograder

The AG for Know Your Tools is out!'2017-01-21 23:59', - Completed '2017-01-22 22:00', '2017-01-23 22
- An instructor thinks this is a good note
1/22/17

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Who IS Carl Evans?

How do we know that Professor Evans is not ACTUALLY a time-traveling Kurt Russell from 1982?
- An instructor thinks this is a good note
1/22/17

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If no input file, what to return?

I can't find any specification of what secure_move should print or return if input file <path> does not exist.
1/22/17

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Using GDB

I ran gdb --args ./secure_move-debug after compiling my code with make debug. My question is how do I then run another f
1/22/17

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Connection Timeout

I tried to ssh to the VM, but in putty, it shows Network Error: Connection Time out. Then, I tried to use my Ubuntu. It
1/22/17

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final_sol bug???

According to the course website the format of the solution should be: <first 5 lines> <newline> <last 5 l
1/22/17

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HW0:submission

How can I know and check whether I have submitted HW0 successfully? Since I don't receive any response email when I
1/22/17

2
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autograder

Is there a way to check if our code is working properly, aside from waiting for the autograder?

▾ Week 1/15 - 1/21

1/21/17

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Cannot use gedit on VM through ssh from own device

Hello! I am trying to open gedit GUI on VM when I ssh to it from my own windows laptop. I have installed Xming and confi
1/21/17

0
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Number of Bytes Allocated?

In lecture, there were a certain number of questions about how many bytes would be allocated for different declarations,
1/21/17

2
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Instr Peer Tutoring: Preemptively Scheduled!

Office Hour Schedule Check it out here: https://illinois-cs241.github.io/help.html (starting next week!) As you vent
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1/21/17

2
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Autograder Schedule?

I'm looking for the autograder schedule to see when it'll be run for the lab and can't seem to find it on th
1/21/17

10
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Things in svn don't change!!!

Hi, I'm wondering why when I have finished submitting the lab, my file "final.txt" has changed but my functi
1/21/17

4
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What does reset_file() do?

Hi, in shred.c in the lab, there is a line that looks like: reset_file(fd); where fd is an int. I have tried googling r
1/21/17

6
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variable does not (post-)decrement in a for loop

In shred.c write_random function, there are following code: char *buffer; for (; num_bytes > 0; num_bytes -= PAGE_
1/21/17

2
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program does not run normally on VM

Hi, I wrote the program on local environment (EWS) and it runs normally (replaced orignal file with random bytes) but on
1/21/17

5
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Are we supposed to edit the code in .c files for this lab?

Is our debugged submission is supposed to contain modified code to the .c files? I'm a bit confused on exactly what
1/21/17

4
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Confused on how to run valgrind

valgrind ./secure_copy-debug files/final.txt files/final_test.txt when i enter that into the terminal it says that secur
1/21/17

4
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Test case 'testFileNotFound'

The description for this test case is Description: Test with high probability that there is random output which is the
1/21/17

2
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print

How would you print '\n' not new line but actually the two characters: \ and n
1/21/17

0
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error: invalid use of flexible array number

error: invalid use of flexible array number what's this error and how to avoid it?
1/21/17

0
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Why no file content shown when cat message.txt?

Was doing "Writing to files - 1" exercise on vm with the following code: #include <unistd.h>#include <
1/21/17

7
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X Connection Not Working Somehow

Hello. I have Putty and Xming installed and configured. I have both Gedit and Sublime installed on my 241 VM. When I use
1/21/17

0
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Instr Impromptu Office Hours!

Hey all, I heard there has been a lot of confusion over HW0, the lab, getting set up with the course etc. This course i
1/20/17

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gdb inferior 01

so I ran gdb ./secure_move files/final.txt files/final_out.txt (gdb) break read_wrap.c:58 Breakpoint 1 at 0x401013: file
1/20/17

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dprintf vs fprintf?

I had a question in today's lecture but I forgot to ask: What's the difference between dprintf and fprintf? Than
1/20/17

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terminal: make (error)

I have moved my terminal's working directory to know_your_tools, then enter "make reset" (which runs fine).
1/20/17

3
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2 Questions on add_line() code in read_wrap.c

I have 2 questions about line 16 of read_wrap.c input->lines[input->num_lines++] = strdup(line); Question
1/20/17

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Lecture Handouts

Are we going to have handouts for each lecture, if so are they posted somewhere online?
1/20/17

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Null characters middle of file

When writing to a file, is it bad practice to have null characters interspersed with the other data or should null chara
1/20/17

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HW0: Create Person

In hw0 when it says "create() should take a name and make a copy of the name and also an age", is create also su
1/20/17

0
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Writing to File

So as I was double checking my HW0, I realized I could have opened the .txt files I made, but in them I have something l
1/20/17

2
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video lecture

Can someone send a link to the video lecture, I can't seem to find one.
1/20/17

0
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Can someone explain this code?

typedef int (*comparator)(void*,void*);int greater_than(void* a, void* b){ return a > b;}comparator gt = greater_t
1/20/17

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Stop talking when the professor is talking, please.

It's extremely annoying and disrespectful.
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1/20/17

4
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attendance

I just want to ask about the attendance policy. So, the policy that if we miss 3+ sections will automatically mean a
1/20/17

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Wikibook in PDF?

Is there a way to convert the wikibook to pdf? I'd like to highlight while I read it.
1/20/17

0
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Problem with "cat" command after writing over final.txt

final.txt is the same size in bytes after running secure_move (9798 bytes both before and after), but cat final.txt give
1/20/17

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Lab Worksheet Answers

I was wondering if the TA's would be posted an answer key each week for the handouts given during discussion so we c
1/20/17

5
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Test Files Modified

I think I have unintentionally modified final.txt and final_sol.txt. I have update my directory using "svn update -r
1/20/17

0
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HW0 Optional Best C code

#include <stdio.h> int main() { double n1, n2, n3; printf("Enter three numbers: "); scanf(&#
1/20/17

0
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HW0 Optional

#include <stdio.h> #include <stdlib.h> #include <sys/types.h> #include <sys/stat.h> #include <
1/19/17

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No Source Available

Everytime my program hit FILE *file_obj = fopen(filename, "r"); or (read = getline(&file_buf, &n, file_o
1/19/17

0
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HW0 Makefile Question

Hello. There is this question in the last part of HW0: You modify the makefile to generate debug builds and type make a
1/19/17

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How to run gdb lab 1

Hello, Good evening everyone. I was trying to run gdb for the lab know_your_tool. I tried the following: gdb .
1/19/17

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Sublime with putty

I've been trying to use sublime as my text editor for my personal machine however the tutorials I found online didn&
1/19/17

0
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magic number PAGE_SIZE in shred.c

Can anyone please explain what this variable is? I cannot find any related information in the comment sections.
1/19/17

7
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file_size mysteriously returns 0

Hi, I'm doing the know_your_tools lab and I have noticed that file_size(int) returns zero even if I can write to th
1/19/17

9
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Check for wrapped_string?

I'm a little confused. I saw a comment on read_wrap.c that asks us to set a breakpoint there to check whether or not
1/19/17

0
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malloc struct?

struct Link { char * value; struct Link* next; }; typedef struct Link link_t;link_t * result = (link_t *)(malloc(sizeo
1/19/17

2
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Could I know the peer tutoring time?

Hi, I have some questions about the lab. The 241 website says there is peer tutoring sessions every week, but I do not s
1/19/17

0
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Can we use root@sp-17 in the VM?

Gedit seems to working better when I am in root
1/19/17

3
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testFileNotFound

Is there a specific way missing files should be handled? e.g. calling perror, exit codes, printing the usage, etc. It
1/19/17

19
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Using GUI programs through SSH

Is there a possibility to SSH from Windows to the Linux server and use the GUI programs/text editors (like gedit) via re
1/19/17

4
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What does "testRandomBytes" do?

What are "random bytes?" What should our code accomplish? EDIT: It is one of the test cases with description
1/19/17

2
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How can I get a new grade report?

I committed a revision to svn. The codes have been updated on svn, but grade_report.html is still showing the result of
1/19/17

8
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C Pointer and Array Questions

Hi, I have a couple of questions from reading the wiki book (https://github.com/angrave/SystemProgramming/wiki/C-Program
1/19/17

1
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Instr SVN and VM Setup

I have talked with Engineering IT and can now explain how the process works for students who have registered after the i
- An instructor thinks this is a good note
1/19/17

0
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hw0

how do we save our responses? or this is a one-time-go type ?
1/19/17

0
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Autograder Frequency

How often does the lab autograder run before the deadline?
1/19/17

0
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How do we join Honors?

Do we join honors by registering for a course? Does the honors section add credit hours to our semester course load?
1/19/17

2
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Instr Know Your Tools Deployed!

Hi everyone,The docs for today's lab are up and can be found here; resources can be found on the lab page hereThe ba
- An instructor thinks this is a good note
1/18/17

0
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null scanf

printf("Type the name of the file.\n"); char* name = NULL; scanf("%s", name); A print statement revea
1/18/17

0
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file pointer

the getline() function requires a file pointer as an argument. If we wanted to pass in a file within the same directory
1/18/17

0
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Questions in the VM

While going through the videos and clicking next, I found a few questions above the console. Are we meant to do those. I
1/18/17

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online ide?

one of the TAs told me to use an online IDE for HW0. Where is it?
1/18/17

0
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Compiling HW0 first problem

I've compiled my code for the first homework problem, but every time I do so I have the following header file that p
1/18/17

0
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"Take your program from "Writing to files" and replace it with printf()"

Does this mean to simply have printf() print "Hi my name is "to the console, or to use it to create a file calle
1/18/17

0
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Terminology question on arrays

By "array," do we mean the column of memory spaces, or the pointer that points to its first element? For examp
1/18/17

0
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HW0 information not showing up

The code portion of the VM is not showing up on the page. Is it supposed to?
1/18/17

3
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Are all variables (different scopes) placed in the same heap?

If one variable is declared outside main(), another is declared inside main(), and another is declared in an arbitrary f
1/18/17

0
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when hw 0 due

I registered this course a little bit late and was wondering that when hw0 is due?
1/18/17

0
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Pointer to an array of Pointers to People

Hello. On page 7 of HW0, there is a question that asks us to construct a Person struct containing a pointer to an array
1/18/17

0
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Honor Section Workload

What do we do in the honor section? Is it a lot more work than the normal section? Thanks!
1/18/17

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HW 0 Due Date

Just to confirm, HW 0 deadline is extended for everyone? And till when?
1/18/17

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Instr Recordings of Lecture

The lecture recordings are now up and should be consistently available shortly after each lecture at the following link.
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1/18/17

0
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How to understand "insufficient to generate new build"?

On Homework 0, there is a question asking: You modify the makefile to generate debug builds and type make again. Explain
1/18/17

0
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Question about close() and open()

int main(){ close(1); int fdes= open("hello.txt", O_CREAT | O_TRUNC | O_RDWR, S_IRUSR | S_IWUSR); if(fdes==-1
1/18/17

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Will lectures be recorded?

^^
1/18/17

3
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hw0 question

the hw looks like a survey. are we supposed to try to compile it and make sure it works before we submit it on the webpa
1/18/17

4
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What IDE does Angrave use?

Does anyone know what's the IDE Angrave used in his videos?
1/18/17

2
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Pointers to Environment Variables

I watched Angrave's video on environment variables but I am still confused as to where their pointers are stored. Wh
1/18/17

3
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include statements for code

Do we need to have any of our include statements in our responses on the google form? In order for the code to compile,
1/17/17

5
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online vm: message on errors

When I run the following code: struct Person { char* name; int age; struct Person** friends; }; typedef struct Pers
1/17/17

0
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CBTF signups

Have CBTF sign ups opened yet? My account seems to be freezing on the "course add" page.
1/17/17

5
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free dynamically allocated array memory

Hello, Good afternoon! I am wondering if the free() takes care of the case where the pointer is an array. In C
1/17/17

3
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Why the output from the computer's compiler is different than the online compiler?

I'm doing the homework and trying to run the c code on my computer, but I get different output for the exactly same
1/17/17

0
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HW 0 Fails to compile...

In HW 0, I can't compile anything. I run code identical to the code given in the video. I get the error: "
1/17/17

2
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how long is hw0 going to take?
1/16/17

1
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pointer to array of pointers to structs

If I declared a pointer to an array of pointers to structs like this: struct MyStruct** s; and I knew that I wanted the
1/16/17

0
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Length of argv

Hello everyone, I was watching the lecture video for HW0 about program argument variable. I am
1/16/17

0
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Lessons and VM pages not working in Chrome

When I click the links to lessons in the Google form, it links me to the github.io page, but the substance of the page i
1/16/17

0
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HW0 specification

Hello everyone, I wish you all have had a great winter break and are ready for the new semester.
1/16/17

1
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Compiling on Browser HW0

I've started up the pre-class HW, and after compiling and getting the first one to work, I tried compiling the secon
1/16/17

0
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How to use CS 241 VM natively?

Hello. I just received the email from EngrIT about the virtual machine I was given for this course. I have a Windows PC
1/15/17

1
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Best and Worst C code

Worst: this battleship code in C http://pastebin.com/88MDNHe3 Best: inverse sqrt code found in Quake 3 float Q_rsqrt(

▾ Week 1/8 - 1/14

1/14/17

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Can we have a save button on the google form?

I lost all my work of hw0. :-(
1/13/17

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Online VM Shell Issues

Whenever I try to run something in the online VM (in this case for activity 1), I see the following output: After thi
1/13/17

5
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Online VM editor adding broken includes

Upon trying to write some code with write(), it constantly includes the following line: #include <asm/dsp56k.h>
1/13/17

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Online VM and Site Doesn't Work if Google Analytics Doesn't Load

As the title. Upon unblocking google analytics, a hard reload will cause the page (either VM or lessons) to function. Re
1/13/17

1
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Instr Welcome to CS 241

Hi CS 241,Welcome to System Programming. I'm excited to be your instructor this semester and to meet you personally
- An instructor thinks this is a good note

▾ Week 1/1 - 1/7

1/7/17

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Welcome to Piazza!

Piazza is a Q&A platform designed to get you great answers from classmates and instructors fast. We've put together thi

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